James Cameron plunged nearly 11km (seven miles) down to the deepest place in the ocean.

Map showing the location of the Mariana Trench...

Map showing the location of the Mariana Trench, designed as a replacement for Image:Mariana_trench_location.jpg. (Photo credit: Wikipedia)

Hollywood director James Cameron has returned to the surface after plunging nearly 11km (seven miles) down to the deepest place in the ocean, the Mariana Trench in the western Pacific.He made the solo descent in a submarine called Deepsea Challenger, taking over two hours to reach the bottom.He spent more than four hours exploring the ocean floor, before a speedy ascent back to the surface.His craft was kitted out with cameras so he could film the deep in 3D.

This is only the second manned expedition to the ocean’s deepest depths – the first took place in 1960 when US Navy Lt Don Walsh and Swiss oceanographer Jacques Piccard spent about 20 minutes on the ocean floor in a bathyscaphe called the Trieste.


Underwater Dive Slates.

What do you use yours for?

For most people,  underwater communication consists of a mixture of hand signals and notes scribbled on an underwater dive slate. This blessedly silent device has other uses as well.

Underwater Navigation – You can turn your dive slate into a mini map to help you navigate your way around the reef and back to your dive boat.
In fact, you can  have a compass built into them to facilitate this purpose.
Of course, you don’t have to painstakingly draw a reproduction of the reef. All you need to do is draw key landmarks and write down your bearing when you turn at one of those landmarks.
Using a dive slate to help with navigation will eliminate your need to do frequent “boat checks.”

Taking Notes On Your Dive – If you like to record every interesting detail about your dive, you might want to keep a dive slate around to jot down items of interest so you can transfer your notes to your dive log.
Even if you’re not interested in taking notes on your dive, it’s a good idea to write down your maximum depth and dive times especially when you plan on performing multiple dives over multiple days.

Test Yourself For Narcosis – This is a little trick deep divers use to make sure their judgment isn’t affected by nitrogen narcosis.
You write a series of basic math problems on your dive slate at the surface and then you perform those problems when you hit your target depth to see how much the depth is affecting your judgment. This test is usually done on preparatory dives to make sure you can handle your target depth under normal circumstances and the test is usually timed.

Recreational scuba divers have access to a mind-boggling assortment of high-tech safety gear, but underwater voice communications equipment is expensive and rarely found outside the ranks of professional, technical and commercial divers. This limits recreational divers to communicating with simple hand signals, and through messages written on plastic dive slates. You can save the expense of a commercial scuba wrist slate by constructing your own.

Ideas for Dive Slates material if you want to make your own:

Most scuba diving slates come with a short golf type pencil.
Another idea I have seen which I think will work really well is a carpenter’s pencil. A 2B pencil also work nicely.

Some type of rubber tubing is needed for your diy dive slate. It will attach the pencil to your slate. There are several options here. You could use medical tubing, surgical tubing, aquarium tubing – essentially any type of flexible tubing that has a hollow center small enough to hold your pencil securely.

Plastic Writing Surface

  • Plastic license plate blanks
  • Vinyl mini blinds
  • Old floppy disks
  • White vinyl siding


Dive slates are relatively inexpensive pieces of equipment and they’re something that every diver should have and if you should try your hand at making your own dive slate you can find instructions at:

How to Make a Wrist Slate for Scuba
By Matt Foster, eHow Contributor | updated August 19, 2011





Why Does Spit Keep a Scuba Mask From Fogging?

User:Darthgriz98's soft-silicone strapped SCUB...

Image via Wikipedia

Before diving, people apply spit or commercial defog solution to the inside of their masks to keep them from fogging. But why does it work?

Spit  makes it hard for water molecules to form fog particle. Spit forces its way between the water molecules and makes them lose their grip on each other, causing them to spread out.

When a mask has been spit in, water can only form large, spread-out droplets because of the reduced surface tension. The large droplets are comparable in size to raindrops and do not stick to the mask in a fog. Instead, they roll to the bottom of the mask, leaving the glass clear.

This is why after a dive, divers can find a small amount of water in the bottom of their masks (provided they didn’t clear the masks during a dive). Masks will fog more in humid environments or when a diver breathes into the mask.

6 Ways to Prevent a Scuba Diving Mask From Fogging

New Scuba Diving Masks:

1. The Toothpaste Trick:
Squirt toothpaste on the inside of the lens and rub it around with your finger or a soft cloth for a few minutes. The simpler the toothpaste, the better, so try to find a paste without bleaching agents . It may help to leave toothpaste in the mask overnight or to scrub the mask several times to allow the chemicals to react. Avoid using an extremely abrasive toothpaste or rough cloth, as these can scratch the inside of the glass.
2. The Flame Trick: Run the tip of a flame over the inside of the lens until the glass turns black, the flame will burn the residue off. A lighter or a tapered candle works well. Once the inside of the mask lens is totally black, wait for the mask to cool and wipe away the soot with a soft cloth. Repeat this process two or three times until it is difficult to get the glass to turn black. Do not allow the glass to become extremely hot, and do not attempt this trick on masks with plastic lenses. Be sure to keep the flame away from the soft silicon skirt of the mask as it will melt with very little heat.

Used Scuba Diving Masks:

Masks should be treated before every dive.

If treatment with a defogging agent does not prevent the mask from fogging, it is possible that some residue is left over from the manufacturing process. Try the toothpaste or flame tricks to remove the remaining residue.

Any agent that prevents condensation from adhering to the inside of the mask’s glass will keep the mask from fogging.

1. Spit: Spit on the inside of the mask and rub it around with your finger. Dunk the mask briefly in fresh water. The goal is to leave thin layer of saliva on the inside of the glass. Spitting does not work well if the mask dries out before diving, so use this technique immediately before the dive.

2. Commercial Defogging Agents: Commercial defogging agents are specifically designed to coat a mask’s lens. Put a few drops of the defogging liquid in the mask, rub it around with a finger, and rinse briefly with fresh water. Remember, the idea is to leave a thin layer of the defogging agent inside the mask, so do not rub out the defog when rinsing the mask.

3. Baby Shampoo: Baby shampoo can be used just like commercial defogging solution.  A few drops rubbed into the lens and then briefly rinsed out will keep a mask from fogging. Baby shampoo is preferable to standard shampoo, as it is generally biodegradable. Baby shampoo smells good, too.

4. Toothpaste: Rub a non-abrasive toothpaste on the inside of the mask lens until it coats the glass completely. Rinse the mask gently with fresh water until the lens is clear. If a diver is highly sensitive to minty fragrances, the air inside the mask may burn his eyes or cheeks during the dive. Before diving for the first time after using toothpaste as a defogging agent, wear the mask for a few minutes to make sure the fragrance is not irritating.


How Well Should A Diver Be Able to See Underwater? – By Natalie Gibb

Chilly scuba diving in New Zealand

Chilly scuba diving in New Zealand (Photo credit: TheCreativePenn)

At what point should a diver take steps to correct his underwater eyesight?

Depending upon the dive, slightly blurry vision at a distance may not present a problem. Many times, poor underwater visibility doesn’t allow divers to see very far anyhow. However, if a vision problem impairs a diver’s ability to read his submersible pressure gauge or see his dive buddy’s hand signals, the diver should consider correcting his vision with either a prescription mask or soft contact lenses.

The Magnifying Properties of Water May Correct Mild Eyesight Problems:
If a diver has a very mild vision problem, the natural magnifying properties of water may correct his vision enough that it does not present a problem while underwater.

Can I Scuba Dive With Eyeglasses?:
A diver cannot wear his everyday eyeglasses underwater for the simple reason that earpieces of the eyeglasses will not allow the mask skirt to seal on the diver’s face. Even if a mask could seal over eyeglasses, the pressure of the scuba mask on the nosepiece and the lenses of a diver’s eyeglasses could cause them to grind into the diver’s face. Instead of eyeglasses, many divers use masks with prescription lenses.

Can I Scuba Dive With Contact Lenses?:
According to the Diver’s Alert
Network (DAN), scuba diving with soft contact lenses rarely causes
problems. However, DAN advises against diving with hard or gas permeable
contact lenses as they may suction painfully to the eye due with the
increased pressure underwater, or may cause blurry vision when air
bubbles becomes trapped between the lens and the eye.
When diving
with soft lenses, a diver should be sure to close his eyes if he floods
or removes his scuba mask to avoid accidentally washing the contact lens
away.  A diver who uses contact lenses should also consider bringing
contact lens rewetting drops along to the dive site. Rewetting drops
will help in the extremely rare event that a diver’s soft contact lenses
become stuck to his eyes from the increased pressure of the dive.

Scuba Diving with Prescription Masks:
Most scuba diving equipment manufacturers offer masks that can be ordered with prescription lenses. Some non-prescription masks may be modified by removing the stock lenses and replacing them with prescription ones.


Diving After Eye Surgery:
Diving is possible after most types of corrective eye surgery. Before returning to the water after eye surgery, a diver must allow time for his eyes to fully recover.  A diver should attend a follow up consultation with his doctor to confirm that his eyes have fully healed before returning to the water.
Any surgical procedure that compromises the structural integrity of the eye may be a contraindication for scuba diving. Surgeries which involve cutting the eye (as opposed to laser procedures) and surgeries for serious conditions such as glaucoma may weaken the strength of the eye. Consult a ophthalmologist before diving if you have had eye surgery for a serious eye condition.

Bi-Focals for Diving:
A diver who requires reading glasses to clearly distinguish small print  should be aware that small, stick-on magnifying lenses are available for scuba masks. Put one of these tiny lenses in the lower portion of a mask lens to create a bi-focal scuba mask!

The Take-Home Message About Scuba Diving with Poor Eyesight:
People with poor eyesight should have no trouble scuba diving. Soft contact lenses, prescription masks, and stick-in bifocal lenses can correct a diver’s vision underwater. In most cases, a diver who has had corrective eye surgery may safely dive, provided he has confirmed with his doctor that his eyes have fully healed.

Don’t let poor eyesight stop you from seeing the underwater world!

Why Does a Wetsuit Keep a Scuba Diver Warm?:

Wetsuits slow heat loss underwater by trapping a thin layer of water against a diver’s body. While the diver still gets wet, his body rapidly heats up the thin layer of water trapped against his body to nearly body temperature. If the suit fits properly, the warm layer of water does not circulate away from the diver’s body. The warm layer of body temperature water conducts less heat away from the diver than the cooler surrounding water, which keeps the diver warmer than he otherwise would be.

Wetsuits are not perfect.
The warm layer of water trapped against a diver’s skin still conducts some heat away from the diver’s body, and it loses some of its warmth through the wetsuit. Given enough time, a diver wearing a wetsuit may still become chilled, depending upon the type of wetsuit. In colder temperatures or on very long dives, a wetsuit may not be sufficient to keep a diver warm.

Consider the following when selecting a wetsuit for a given dive environment:

1. The Tighter the Wetsuit, the Warmer You Will Be:
A wetsuit keeps a diver warm by trapping water inside the suit. A snug suit will more effectively trap and hold water against a diver’s skin than a loose suit. A wetsuit that does not fit snugly will allow cold water to circulate into the suit, which will cause the diver to become chilled more quickly. Tighter is better – up to a point. A suit that is too tight across the chest will restrict a diver’s breathing, which can be uncomfortable and even dangerous.

2. The Thicker the Suit, the Warmer You Will Be:
Underwater, heat is lost through the neoprene layer of a wetsuit. The thicker the wetsuit, the less heat will be lost and the warmer the diver will be. However, thicker wetsuits tend to restrict movement, so divers will be most comfortable choosing the thinnest suit that will keep them warm in the anticipated dive environment.

3. The Deeper You Dive, the Colder You Will Be:
The neoprene rubber in wetsuits is lightweight and flexible because it is manufactured with millions of tiny air bubbles sealed inside the rubber material. Because these air bubbles are completely sealed, the air inside them will expand and compress according to Boyle’s Law. The deeper a diver descends, the more the air bubbles compress and the thinner the wetsuit becomes. Because a thinner wetsuit is less insulating, the deeper a diver goes, the colder he can expect to be.

4. The Longer the Dive, the Colder You Will Be:
While wetsuits do help to slow heat loss underwater, a diver’s body still gradually loses heat over long periods of time. After long dives, a diver may feel chilled from this slow heat loss. Select a thicker suit for longer dives.

5. Natural Insulation:
While a diver’s “natural insulation” is not a characteristic of the wetsuit itself, a diver’s body fat will affect how rapidly he chills underwater.  Divers with a low body fat percentage will cool more quickly than divers with a normal percentage of body fat. Divers who have very little body fat may want to consider choosing a thicker suit than average divers diving in a similar dive environment.

6. Short Suits vs Long Suits:
Short wetsuits expose a diver’s lower legs and arms to the water. Short wetsuits still help to keep a diver comfortable in warm water because they cover the diver’s torso. They are not as effective as long suits because more of the diver’s skin is exposed to the water.

A good wetsuit slows heat loss underwater to the point that a diver remains comfortable throughout a dive. Consider characteristics such as wetsuit thickness and fit, as well as the length and depth of the dive when selecting a wetsuit for a given dive environment.