Underweighting can be just as dangerous as overweighting.

scuba diver in lotus position

Equipment and the Environment Will Both Affect Your Buoyancy

Wetsuits, tanks, and even accessories and tools will affect your buoyancy. Whenever you change one of these items, it is necessary to complete a buoyancy check to determine the effect of the new item on your buoyancy. The salinity of the water will also affect a divers buoyancy. The obvious example is buoyancy in fresh water vs salt water, but keep in mind that the salinity of the ocean may also vary in different regions of the world, and you may need slightly more or less weight depending upon your dive location.

Conducting a weight test before a dive can make the difference between a miserable dive and an enjoyable one.

 

Conduct a Buoyancy Check Before DivingScuba 2

Test your buoyancy in a new location or whenever diving with a new piece of gear. Most of the time, diver’s have a limited number of dives on vacation, and it is worth the effort to make every dive comfortable and safe.

In fact, most dive operators will be thrilled if you ask to wade into the ocean or hop of the pier before your first dive to double check your weighting.

 

The general rule of thumb for proper weighting is that with all of his gear in place, with a nearly empty tank, a diver who completely empties his BCD and holds a normal breath should float at eye level. When he exhales he should sink.

 

Remember!! As the tank empties, it will become positively buoyant.

If you can empty your BCD, hold a normal breath, and float at eye level at the beginning of the dive, you will not have enough weight to comfortably maintain neutral buoyancy at the end of the dive.

The problem here is that most dive shops are not in the practice of providing nearly empty tanks for buoyancy tests. There are two solutions to this:

 

  1. Conduct the buoyancy test with a full tank as outlined above, and then add the appropriate amount of weight to offset the buoyancy swing of your tank as it empties.
  2. Conduct the buoyancy test as outlined above with a full tank, but instead of checking that you float at eye level, check to see that you sink slowly while holding a normal breath.

 

Double Check Your Buoyancy at the End of a Dive

Once you have successfully completed a dive with enough weight to keep you comfortably below water the entire time, it is a good idea to double check your weighting at the end of the dive.

To do this, purge your regulator gently until you are down to about 500 psi or 30 bar. Then, on the surface, conduct a buoyancy check before exiting the water. Do you float at eye level and sink when you exhale?Scuba 3

Do you have to swim to get down? Float like a balloon on the surface? Add a little weight on your next dive.

Do you still sink while holding your breath? Remove a few pounds and try again on the next dive.

 

Adding a Small Amount of Air to Your BCD During Descent Is Good

Many divers seem pleased that they can descend and arrive at the planned depth without adding air to the BCD.

Again, this is not a desirable situation. Because most tanks become more positively buoyant throughout a dive, divers who do not need to add air to their BCDs during descent to establish neutral buoyancy are likely to be underweighted.

 

I Don’t Need to Add Air During Descent. I Am Fine at the End of the Dive!

These are the people who have exceptionally low air consumption rates, and surface with at least half of their air remaining. Yes, they can be perfectly neutral during their safety stops, and they don’t go flying to the surface like awkward buoys at the end of the dive. Their tanks have not become positively buoyant because they haven’t breathed enough gas to cause a buoyancy swing.

 

The problem with this habit is that it does not prepare divers for an emergency situation, when they are low on gas because they over-breathed a tank due to a stressful situation, surface with less gas than normal due to an unforeseen occurrence, or are forced to share air with another diver.

In these situations, such a diver will have trouble staying down, and of course, these are the situations when having enough weight can make a big difference between an annoying situation and an uncontrolled ascent to the surface.

Plan for the worst case scenario: a low tank and increased breathing rates due to stress.

 

Diving with less weight does not make you a better diver.

Diving with the correct amount of weight does.

Slight overweighting is correctable: just add a little air to the BCD.

To be safe on dives, proper weighting is key.

Take the time to get your weighting right and you can avoid many potentially dangerous situations and dive more comfortably.

“Save a Dive” Kit

SaveaDiveKit

 

Save a dive kits may be a small as a zip-lock bag or as big as a tool box, a diver’s save a dive kit will differ depending upon his needs and type of diving.

Suggested parts for the Basic Save a Dive Kit:

Spare mask strap
Mask straps are one of the most common items to break before a dive. Be sure to select a spare mask strap that fits your mask.

Spare fin strap and buckle
Fin straps break less frequently than mask straps, but they do break.  Be sure to choose the correct strap for you fins.

Spare regulator mouthpiece and zip tie/cable tie to secure it.

A spare regulator mouthpiece is an absolute essential.

Basic o-ring kit
This should include o-rings for low pressure and high pressure hoses, as well as o-rings for yoke tank valves or o-rings for DIN regulators (depending upon which you use).

High pressure and low pressure port plugs for the regulator first stage.

When a diver removes a hose from his regulator first stage, he must plug the hole with a port plug. Bring along both a high pressure and low pressure port plug that fits your first stage (apex first stages have unusually large port plugs).

Small adjustable crescent wrench
This is used to remove hoses from the regulator to replace o-rings.

Hex wrenches/ allen keys
Hex wrenches are used to remove port plugs, as well as for a variety of other applications.

Cutting device/knife
At a minimum, your cutting tool should be able to cleanly slice off zip ties and snip strings and bungee.

Needle nose pliers
Needle nose pliers are great for just about everything that needs to be pulled or tightened.

Small pot of silicon lubricant

This is used for greasing o-rings in dive gear, dive lights, etc.

A lighter

Zip ties and duct tape

Nail clippers

Nail clippers are useful for nipping of zip ties and clipping small items.

White trash bag.
Use a white plastic trash bag as a work surface on dirty or wet areas. This makes seeing o-rings and parts easier, and keeps them clean and dry.

Dry suit zipper wax.

Essential if you use a dry suit.

A DIN-to-yoke or yoke-to-DIN adaptor

This allows you to dive with both DIN and yoke tanks.

• Bungee/ Shock Cord

Bungee can be used to secure lights, create necklaces for back-up regs (long hose configuration), manufacture watch/computer straps, and create octopus/alternate air source holders.

 

 

 

Buoyancy Basics – Seven Ideas for Adjusting Trim Without Adding Weight

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Before making any adjustments to his gear, a diver must first check his trim. He should enter the water with all of his diver gear and attempt to hover in a horizontal position without moving his fins or arms. He can then note whether he has a tendency to hover head or feet up, or to roll to one side.

1. Move Weights Around

Changing the position of a diver’s weights may help to adjust his trim. Many buoyancy compensators (BCs) have trim weight pockets just below the diver’s shoulders. A diver who tends to float head-up may use the pockets to redistribute his weights, placing a few pounds in each pocket. For example, a diver who uses ten pounds of weight may want to carry six pounds on his weight belt and four pounds (two on each shoulder) in his trim weight pockets. If a diver’s BC does not have trim weight pockets, some divers will place a weight on the BC’s tank band for a similar effect.

Redistributing weights is not always possible, as in the case of a diver who uses very little or no weight, or a diver who uses a BC without trim weight pockets. Some divers simply find that redistributing weight does not correct their trim. Fortunately, it is possible to manipulate other pieces of dive gear to perfect a diver’s trim.

2. Tank Position

A diver’s tank position affects his trim. A tank can be lowered or raised in relation to a diver’s BC by changing the position of the BC strap on the tank. A diver who attaches his BC strap near the top of his tank will find that the tank sits low on his body. This may help to correct for a foot-up position by shifting the weight of the tank towards the diver’s feet. Attaching the BC to a lower part to the tank will have the opposite effect.

3. Reposition the Buoyancy Cell

Some equipment configurations, such as a backplate/ wing system, allow a diver to move his buoyancy cell (the part that inflates and deflates) upwards or downwards in relation to his harness. A diver can move the buoyancy cell towards his head to compensate for a foot-up position, or towards his lower body to correct a head-up position.

4. Change Your Neoprene

The thickness and distribution of a diver’s neoprene garments can have a huge effect on his trim. Thick, full-length wetsuits, especially wetsuits that have 5 mm or 7 mm legs, have a tendency to cause a diver to float feet-up. Switching to a wetsuit that has a 7 mm torso and thinner legs can remedy this situation. Similarly, thick wetsuit booties can cause a diver’s feet to float. Simply switching to thinner booties may solve a foot-up position. Finally, warm-water divers who find themselves floating foot-up may consider switching to a short wetsuit, as long as the suit still provides adequate thermal protection.

Adding neoprene layers to the torso may also have a slight effect on a diver’s trim. Thick vests and hoods add buoyancy to a diver’s upper body, and may be useful in compensating for a foot-up position.

5. Change Your Fins

Changing your fins may sound like a drastic step, but switching your fins can often be a helpful method of correcting trim. Different brands and styles of fins have astonishingly different buoyancy characteristics. For instance, SCUBAPRO Jet Fins are some on of the most negatively buoyant fins on the market. Other fins may be neutral or even positively buoyant. Heavier fins can compensate for a foot-up position, while lighter fins can compensate for a head-up position.

6. Change Your Regulator First Stages

Regulator first stages can be very heavy or relatively light. A heavy regulator first stage can help to fix a head-up position, and a lighter regulator first stage can help to compensate for a foot up-position. Of course, regulators should be selected first and foremost for their breathing characteristics, but given the choice between several similar first stages, a diver may want to make his final decision based on weight. The weight of the first stages is of particular interest to technical divers, who use at least two first stages on every dive.

7. Consider Your Accessories

Finally, a diver may want to take a look at his accessories and consider their effect on his trim. A diver who carries a heavy dive light may have a tendency to list to one side — in this case he may want to place other accessories (or counterweight in a worst-case scenario) on the side opposite side of his light. Divers who carry huge, heavy reels on their rear d-rings may notice that they float head-up. Switching to a lighter reel may fix this problem without any other adjustments.

In most cases, a diver’s trim can be adjusted without adding weight. Before making any adjustments, a diver should attempt to hover in horizontal trim with all of his dive gear in place (even accessories) to diagnose any trim problems. He can then begin repositioning or changing dive gear to improve his trim. It is advisable to change or reposition only one piece of gear at a time, and to get into the water after each adjustment to evaluate its effect. It is difficult to determine the result of an individual alteration when several adjustments are made at once.

 Take your time and make methodical adjustments to your equipment, one change at a time, until you are happy with your trim.

Scuba Wetsuit Care 101: Removing Odours & Extending Suit Life – By Christine

75-anniv-wetsuit-7

If you want your wetsuit to last as long as possible, a bit of proper wetsuit care is all you need. The difference between a wetsuit with a 1 year life and 6 year life depends, to a certain extent, on how often you are using it. But to a larger extent, how well you take care of your wetsuit is going to either quicken or slow its deterioration. Below are 13 care tips for extending wetsuit life.

1. Neoprene and Hot Water Are Not Friends

Neoprene loses some of the flexibility when soaked in hot water. So hop in a cold shower with your wetsuit on or only soak it in lukewarm water.

2. Sun & UV Rays Deteriorate Neoprene

Sun and UV rays both cause your neoprene wetsuit to age more quickly. So if you need your scuba suit to dry, don’t try to hasten the process by placing it in the sun. In the long run, the neoprene will become hard and lose flexibility.

3. Don’t Put Your Wetsuit in a Hot Trunk

If your car has been sitting in a parking lot on a hot day, then putting your wet suit into the trunk is not a great idea. This will essentially “cook” your gear, increasing smells and breeding bacteria.

4. Turn Your Wetsuit Inside Out to Dry

To dry your wetsuit, its best to first turn it inside out before hanging it up. By turning the suit inside out, flexibility will be maintained on the outer side. This means that even if the wetsuit it not 100% dry to next time you put it on, you’ll for sure be crawling into a drier side.

5. Carefully Store

Carefully store your dry wet suit on a flat surface or hang on a wide coat hanger in your closet.

6. Quickly Clean & Dry Your Suit

After a dive, don’t let your wet wetsuit sit in your dive bag, all stinky, messy and sandy. Clean the suit quickly and dry it completely before storing away. This type of regular wetsuit care will be sure to increase its lifespan.

7. Avoid “Messy Dressing”

If you’re doing a beach or shore dive, keep your wetsuit up and aware from the mud/ sand. Its not so comfortable to pull on a sandy wetsuit! Also, when you take off your wetsuit, stand on pavement, a rock, your changing bag, grass or anything besides the middle of the sandy beach.

8. Wetsuits Don’t Belong in the Washer

Neoprene wetsuits must be handled with care and can’t be put through the washer and dryer. You have to hand wash and air dry.

9. Can I Iron my Wetsuit? …. No!

It’s a no-brainer that you should not iron your wetsuit. Just look at the rubber areas around the zippers and knees. Also, if you were to iron the neoprene, that amount of excessive heat would make the suit very stiff.

10. Bleach is Off-Limits

Strong washing agents, such as bleach, are way too harsh for your neoprene wetsuit (not to mention the discoloration that will occur). There are some mild cleansing agents, such as “Sink the Stink” and “Trident Wetsuit Cleaner” that you can purchase from your local dive shop, but regular dish detergent will work just as well (read on to find out how to get rid of wetsuit smells on your own).

11. Why Does My Wetsuit Stink?

Your wetsuit can stink if it was left, wet, in a bag for a while and wasn’t rinsed. The smell comes from bacteria that begin to feed on the normal sweat and body oils and odours clinging to the wetsuit after we use it. Also, if you urinate in your wetsuit, the pee can leave an odour behind.

12. How to Get Ride of Wetsuit Smells & Odours

As I mentioned, there are special cleaning soaps and solutions for getting rid of wetsuit odours, but I personally, find that there is an easy, more economical way to erase suit smells.

Here is my home made recipe for washing smelly wetsuits:

1st: Fill the tub up ¼ of the way with fresh, warm (not hot) water.
2nd: Add a couple tablespoons of dish washing detergent, just enough to get a dilute bubbly water bath for soaking.
Note: Some people will use laundry detergent, but I think even that is too harsh for neoprene (and tougher to rinse off). The only laundry detergent to consider using is Woolite.
3rd: Wash your wetsuit in the tub of soap and the detergent will break down the body oils and odours. In addition, it will help wash away the bacteria that caused the smell in the first place .
4th: Rinse your wetsuit in fresh water in order to get all the detergent off. Then hang your wetsuit up to dry in the fresh air (away from direct sunlight).
5th: Every few weeks, repeat this process to keep your wetsuit completely odour-free!

Christine Beggs is the founder of Project Blue Hope, a site dedicated to spreading her wish for a “Future of Blue.” Currently pursuing her Master’s degree in Marine Conservation, Christine is passionate about ocean health and the preservation of coral reefs. Join the discussion about marine issues @ProjectBlueHope and www.ProjectBlueHope.com to help spread the word for more balanced oceans.

How Does a Regulator Work? A Beginner’s Guide to Scuba Regulators By Matt Dunne, Regulator Nerd and Enthusiast

 

Regulator
Scuba diving regulators may seem complicated, but they are surprisingly simple devices.

Few pieces of sporting equipment carry more mystique than scuba regulators. Regulators are sold with a dizzying array of choices, features, and often hype, and there may be a fierce loyalty to brands among experienced divers. But is all the hype justified?

What Does a Scuba Diving Regulator Do?:

Obviously, a scuba diving regulator allows a diver to breathe from a tank underwater. But how does a regulator transfer the high pressure air from the scuba tank to the diver’s lungs at a pressure that will not injure him?

The purpose of a scuba diving regulator is to reduce the high pressure air in a scuba tank to a breatheable pressure on demand.
Scuba regulators are simple devices, and the method in which they reduce high pressure tank air to a breathable pressure is easy to understand. Even the simplest scuba regulators do this adequately, at all recreational diving depths and with remarkable reliability.

Regulator Terminology:regs

To understand how scuba diving regulators work, it is important to become familiar with some basic regulator vocabulary and concepts.

First Stage: The first stage of a scuba diving regulator is the part of the regulator that attaches to the tank valve.

Second Stage: The second stage of a scuba diving regulator is the part that the diver puts into his mouth.

Tank Pressure: The pressure of the air in a scuba tank. Air inside a tank is compressed to a very high pressure in order to carry an adequate supply of breathing gas for a scuba dive. A full scuba tank is often pressurized to 3000 psi.

Intermediate Pressure: The pressure of the air output from the first stage and sent to the second stage. Common intermediate pressures are around 125 – 150 psi above ambient pressure.

Ambient Pressure: The pressure surrounding a diver. Ambient pressure underwater is greater than pressure at the surface because pressure increases with depth. A scuba diving regulator delivers air to a diver’s lungs at ambient pressure. Since the ambient pressure changes as a diver changes depth, scuba diving regulators must adjust the air delivered to ambient pressure as a diver ascends and descends.

How Do Regulators Work?:

Scuba regulators reduce tank pressure in two steps. The first step of pressure reduction is from tank pressure to intermediate pressure, and the second step of pressure reduction is from intermediate pressure to ambient pressure.

The Regulator First Stage:First Stage

The first stage reduces air at tank pressure to intermediate pressure, and releases the intermediate pressure air into a hose which feeds into the regulator’s second stage. The way the regulator first stage reduces tank pressure is ingenious.

1. A first stage consists of two air chambers separated by a valve. When the regulator is not pressurized this valve is open. When connected to a tank, air from the scuba tank flows into the first chamber, through the valve, and into the second chamber. The valve between the two chambers stays open until the air in the second chamber reaches intermediate pressure.

2. Once the air in the second chamber reaches intermediate pressure, the valve between the two chambers closes, preventing the high pressure air from the tank from flowing into the second chamber.

3. When a diver inhales, air from the second chamber is released to the second stage.

4. As the air in the second chamber is released, the pressure in the second chamber drops, allowing the valve between the two chambers to open. Air flows from the first chamber into the second chamber until the pressure in the second chamber rises to intermediate pressure and once again forces the valve between the two chambers closed.

The Regulator Second Stage:800px-Scuba_regulator_2nd_stage_animation

The second stage reduces air from intermediate pressure to ambient pressure so that a diver may safely and comfortably breathe. Another important feature of a second stage is that it allows air to flow to the diver’s mouth only when he inhales. This is a vital feature of scuba diving regulators as a constant flow of air would deplete the tank very quickly.

1. The second stage consists of a single air chamber with a valve in the inlet fitting for the hose from the first stage. This valve stays closed except when a diver inhales, and separates intermediate pressure air in the hose from ambient air in the second stage.

2. The second stage uses a flexible silicone diaphragm to seal water out and air inside. There is a lever that rests against the diaphragm on the interior of the second stage. This lever operates the valve in the inlet fitting.

3. When a diver inhales, he lowers the air pressure inside the second stage by taking some of its air into his lungs. This allows water on the outside to push the diaphragm in slightly, which pushes on the lever, opening the valve, and allowing air to rush in until the pressure equals the outside water pressure, which is ambient pressure.

The simple genius of this design is that the water pressure surrounding the regulator creates the ambient pressure. The result is that the second stage automatically adjusts to the diver’s depth.

 

The Different Types of Dive Flags and When to Use Them

diver_down_flag2

 

 

 

 

 

 

Most divers are familiar with the red and white “diver down” dive flag  For many divers, the image of the diver down flag is a way to advertise their love of diving, but dive flags also fulfil a practical purpose.

What Is the Purpose of Flying a Dive Flag?

Dive flags are used to alert boats and other water craft that divers are in the area, possibly near the surface. The hope is that flying a dive flag will prevent accidental collisions between watercraft and scuba divers. Some commercially available dive flags are attached to floating surface support stations, such as an inflatable buoy or inner-tube. Dive flags also help surface support personnel track the location of submerged divers.

What Do Dive Flags Look Like?

Two main styles of dive flags exist:

The diver down flag and the alpha flag.

They have different applications, and the recommended use of dive flags varies with location.

The Diver Down Flag

Diver down

The diver down flag is the well-known red flag bisected by a white, diagonal stripe. The stripe runs from the upper left corner of the flag to the lower right corner. This flag is used when divers are in the water to alert boats to the possibility of divers near the surface. In most locations, diver down flags should be lowered or removed from the water once the divers have safely exited the water. The flag is recognized in most parts of the world.

The Alpha FlagAlpha flag

The alpha flag is white and blue flag, with a triangular notch on the free end. The left side of the flag is white and the right side of the flag is blue. The alpha flag is recognized internationally and serves a different purpose from the diver down flag. The flag is flown by a boat whenever the mobility of the vessel is restricted. Other watercraft should recognize that the boat cannot move quickly, and should yield the right-of-way to a vessel flying an alpha flag. In the case of scuba diving, a dive boat must stay close to the divers it is tending, and cannot easily move from the vicinity of the people under the water. In many parts of the world, the alpha flag is recognized as an indication that divers are in the area, the flag has multiple uses and it is advisable to fly both the alpha flag and the diver down flag to avoid confusion.

When Should You Fly a Dive Flag?

Dive flags should be flown whenever there is the possibility of boat traffic at or near a dive site. When diving from a boat, a dive team need not carry its own dive flag provided that it stays within a predefined proximity of the dive boat.

When shore diving at sites where watercraft traffic is a possibility, divers should float their own dive flag on the surface, and stay close to the flag. The exact distance varies with location, but it is recommended that divers stay within 10 meters of the dive flag, depending upon the dive site.

How Close Can Boats Get to Your Dive Flag?

Boats and other water craft should stay well clear of dive flags, and should decrease their speed when approaching an area where a flag is visible. The exact distance varies with location. Realistically, however, boats can get just as close as they like to a dive flag. Distracted boaters might not even notice the flag, and some may not be aware of its meaning. Therefore, it is important to visually check the surface and listen for boat traffic before surfacing from a dive, even when a dive flag is properly used.

How Should a Diver Carry a Dive Flag?Diver-Down-flag---Florida-Spiny-Lobster-Regulations---FWC

In situations that require a diver to fly his own dive flag, the diver should tow the dive flag above him during the dive. Commercially available dive flags usually come with a buoy or inflatable raft to keep the flag upright at the surface. The diver tows the flag using a line attached to a reel. The reel should contain a length of line several times longer than the anticipated depth of the dive. Never clip the reel to your buoyancy compensator (BC) or dive gear when it is attached to a dive flag, because you risk becoming entangled in the line or dragged along behind a flag snagged by a boat. Divers who are using a dive flag should also carry a line cutting device in order to cut the line in the event of entanglement. Finally, all dive flags should be stiff enough to remain unfurled and visible without wind.

What Should You Do If You Have to Surface Far From Your Dive Flag?Inflatable diver down marker2

In an ideal world, divers would always surface just underneath their dive flags or very close to the dive boat. However, it is possible that a diver may become disoriented or has an emergency, and have to surface away from the dive flag. For this reason, it is a good idea to carry an inflatable surface marker buoy at any dive site where there is the possibility of boat traffic. The buoy should be attached to a reel, and should be inflated and sent to the surface before the diver attempts to surface. A diver surfacing far from his dive flag or boat should always scan the surface of the water and listen for boat traffic before surfacing.

Inflatable diver down marker

 

Open Water Skill: Disconnect Low Pressure Inflator – From Nicholas McLaren

P61

 

 

Aim: To disconnect and reconnect the low pressure inflator.

 

Reason to Learn: It is possible for an inflator button to become jammed on, causing your BCD to continually inflate. There is an easy solution to this problem – to disconnect your low pressure inflator. Once it is disconnected it is possible to manually inflate your BCD

 

Step One: Hold your inflator with your right hand and grip the inflator hose with your left hand. Grasp the quick disconnect valve between your thumb and index finger, pulling the slide-lock back.

 

Step Two: Pull the low pressure hose away from the inflator. You may hear a loud popping noise; this is just the sound of air escaping from the valve as you remove it from the inflator.

 

Step Three: Now that the hose is disconnected your BCD will stop auto-inflating. You can adjust your buoyancy by releasing air from your BCD by using your deflator or a dump valve.

 

You can now manually inflate your BCD

 

Step Four: In training you will be asked to reconnect your Low Pressure Inflator while still underwater. In the event of a real stuck inflator button it is unlikely that you’d want to do that. However, it is possible that you will resolve the problem of the sticking inflator button once the hose is disconnected and that you’ll want to reconnect the hose. This step is quite similar to when you connect it when setting up your gear, but may be more difficult underwater.

 

Step Five: Gripping the hose with your left hand, use your thumb and index finger to pull the slide lock back.

 

Push the quick release valve back onto the low pressure inflator. It may be difficult as there is air in the low pressure hose. You will need to push down forcefully and when it is all the way down let the quick release valve snap back into place.

 

It is quite common for this to be quite difficult due to air in the line. Don’t be concerned if it takes a few tries to reattach the hose.

 

 

 

Once you’re sure that the hose is reconnected, pull back firmly to ensure that it is definitely connected. If the hose comes loose, repeats steps 3 and 4.

 

 

 

Once the hose is reconnected, test the inflator button to ensure that it is working properly. If is jams again, disconnect it and don’t attempt to reconnect it until it has been serviced

 

English: Line art drawing of an aqualung Hose ...

English: Line art drawing of an aqualung Hose Mouthpiece Valve Harness Backplate Tank (Photo credit: Wikipedia)