Monday, October 22, 2012

Thirteen Things You Didn't Know About Scuba Diving Gear - But Should

Thanks to Darryl Carson and Sport Diver

Divers have an intimate connection to our equipment. But the history, evolution and hidden inner workings of many integral pieces of our collective kit might be a mystery to many of us. Check out these 13 curious details, historical head-scratchers and surprising facts, including why dive watches glow and what the heck is the “Bends-O-Matic?”

One of the earliest “dive computers”, the SOS Decompression Meter, was completely mechanical and simulated the process of gas absorption in the body. Its sketchy performance earned it the nickname “Bends-O-Matic.”

The first decompression tables, and the basis for modern dive computer algorithms, were published in 1908 by John Haldane. They were based on simulated dives using a hyperbaric chamber. The test divers were English goats.

Depth ratings for extreme deep dive watches have exceeded the known depth of the oceans. The Sinn UX is rated to 12,000 meters, more than 1000 meters deeper than the Marianas Trench.

Tritium, a radioactive material safely used in tiny quantities to make illuminated markings in many dive watches, is also used as a “booster” in multi-stage hydrogen bombs.

The rhythmic, mechanical breathing of Star Wars’ Darth Vader is iconic. It’s the amplified sound of a scuba regulator.

Jacques-Yves Cousteau and Emile Gagnan invented the Self-Contained Underwater Breathing Apparatus in 1943. It was based on a diaphragm regulator design first developed more than a hundred years before.

Last year, Allen Sherrod, a dive instructor from Florida, spent 48 hours and 13 minutes breathing from a regulator while submerged off Lauderdale-by-the-Sea, Florida. It was a world record time for a saltwater dive.

Many warm-water divers use their octopus as a defense against stinging jellyfish. A brief purge beneath an oncoming assailant will gently lift it out of the diver’s way.

An ancient bas-relief dating back to 900 B.C. shows Assyrian divers using animal skins filled with air, which they carried with them to increase the length of their dives.

Before the standard power inflator came along, horse collar BCs incorporated small CO2 canisters to provide emergency inflation when needed, just like many personal floatation devices do today.

The popular backplate-and-wing BC design came as a cave diving innovation and improvement over “belly bags,” which uncomfortably sandwiched divers between an air bladder and a pair of heavy steel tanks.

No welding is used in making a typical aluminum scuba tank. Instead, a 32-lb. aluminum slug, 7-inches across, is pressed into shape by 2,500 lbs. of pressure in just 20 seconds.

Everyone knows LED lights are more efficient than incandescent models. But how efficient? Tests have shown burn times may average 30 times longer using identical battery power.

Kathy Dowsett

Sunday, October 14, 2012

Wearing Contact Lenses When Scuba Diving

Avid divers know what an amazing feeling it is to submerge into a world so different from our own. The underwater paradise is the only real frontier left to explore on the planet and even in frequently visited locations, like the Red Sea or Bunaken, you’ll have the opportunity to experience something unique, see fantastically colored fish and impossibly shaped coral reefs.

However, when you are scuba diving, you rely heavily on your sense of sight to take in all the beauty. This means that if live with a vision defect, such as nearsightedness or astigmatism, you will need prescription goggles or, if your wallet doesn’t stretch that far, a pair of contact lenses. So, there is no reason not to get the best experience every time you’re down in the water.

Using Contact Lenses when Diving

It is possible to wear glasses when scuba diving but it’s not the optimal choice when you’re also wearing a diving mask. What we would recommend is to wear contacts while diving. There are a couple of things to consider when you wear lenses underwater.
■If you experience mild discomfort, perhaps feel as if the lenses tighten a bit while you’re down, simply use lubricating eye drops before and after each session. This should relieve some of the irritation.
■Another thing to think about when diving with contact lenses is that you should blink as much as possible. In doing so you’ll prevent bubbles from forming underneath your lenses – these bubbles are in no way harmful to your eyes but they can cause minor discomfort and blur your vision.
■Also, when you clear your mask of water, remember to close your eyes so that you don’t lose your contact lenses!

Which Lenses to Wear

As most contact lens wearers know, there are two types of lenses; hard contacts and soft contacts. When diving, it is recommended to wear soft contacts, due to the fact that soft contacts contain a percentage of salt water which helps prevent them from floating off your eyes if they are open when you flood your mask. Hard contacts (gas-permeable) are more likely to simply disappear off your eye into the water, and it’s next to impossible to find a lost lens under water due to their inherent translucency. This is why you should always wear disposable lenses when doing water activities, since an eventual loss is not that great.

More to Think About

You shouldn’t worry about wearing contact lenses when scuba diving – it is perfectly safe. But, eye care experts suggest the following tips to keep in mind when using lenses
■When using contacts it’s important to ascend slower than normal.
■Wear soft contact lenses.
■Rinse lenses between dives to get the salt water out.
■Bring an extra pair if a problem should occur.
■Let your diving buddy know you’re wearing contacts so that he or she can retrieve your mask if you should lose it.

Other than this there is really nothing special to think about when hitting the water –simply dive right in!

Thanks to Scuba Diving

Kathy Dowsett

Monday, October 8, 2012

Return to Antikythera: Divers revisit wreck where ancient computer found

Thanks to:
Jo Marchant is the author of a book about the mechanism, Decoding the Heavens: Solving the Mystery of the World's First Computer

In 1900, Greek sponge divers stumbled across "a pile of dead, naked women" on the seabed near the tiny island of Antikythera. It turned out the figures were not corpses but bronze and marble statues, part of a cargo of stolen Greek treasure that was lost when the Roman ship carrying them sank two thousand years ago on the island's treacherous rocks.

It was the first marine wreck to be studied by archaeologists, and yielded the greatest haul of ancient treasure that had ever been found. Yet the salvage project – carried out in treacherous conditions with desperately crude equipment – was never completed. So this month, armed with the latest diving technology, scientists are going back.

Antikythera Mechanism
Between 1900 and 1901, the sponge divers retrieved a string of stunning antiquities, including weapons, jewellery, furniture and some exquisite statues. But their most famous find was a battered lump that sat unnoticed for months in the courtyard of Athens' National Archaeological Museum, before it cracked open to reveal a bundle of cogwheels, dials and inscriptions.

It has taken scientists over a hundred years to decode the inner workings of those corroded fragments, with x-ray and CT scans finally revealing a sophisticated clockwork machine used to calculate the workings of the heavens.

Dubbed the Antikythera mechanism, it had pointers that displayed the positions of the sun, moon and planets in the sky, as well as a star calendar, eclipse prediction dial and a timetable of athletics events including the Olympics.

It's a stunning piece of technology that revolutionises our understanding of the abilities of the ancient Greeks. Nothing close to its complexity is known to have been created for well over a thousand years afterwards, and the emergence of mechanical clocks in medieval Europe.

There are questions that remain unanswered, such as where it's from and who built it (Posidonius, a philosopher who lived on Rhodes during the first century BC, is one candidate, while the third century BC genius Archimedes may have invented this type of device). But one of the most intriguing mysteries relates to the wreck on which it was found. What's still down there?
The wreck lies in around 60 metres of cold, rocky, current-swirled water – not an easy place to visit. The sponge divers who salvaged its cargo worked in clunky metal diving suits with little understanding of the dangers of diving at such depth. By the time they abandoned their project, two of them had been paralysed by the bends, and one was dead. They left behind stories of abandoned treasures, including giant marble statues that rolled down the steep slope from the wreck and out of reach.

The undersea explorer Jacques Cousteau spent a couple of days at the wreck site in 1978 and brought up some precious smaller items, including some coins from the Asia Minor coast, which suggested that the ship sailed from there around 70-60 BC (probably carrying war booty from Greek colonies back to Rome). But even with their sleek scuba gear, Cousteau's divers could spend only brief minutes on the seabed without risking the bends.

No one has been back since. Now, after years of negotiations with the Greek authorities, Brendan Foley, a marine archaeologist based at Woods Hole Oceanographic Institution in Massachusetts, finally has permission to dive at Antikythera. He's working with Greek archaeologists including Theotokis Theodoulou of the Ephorate of Underwater Antiquities.

This week, the team begins a three-week survey using rebreather technology, which recycles unused oxygen from each breath and allows divers to stay deeper for longer. The aim is to survey the wreck site properly for the first time, to find out once and for all what has been left down there – and to check down the slope, to 70 metres depth or more, to see if those stories of runaway statues are true.
Any items found on the wreck site could provide further clues to the origin or ownership of the ship. And not all of the pieces of the Antikythera mechanism were ever found. It's a long shot, but those missing bits could still be on the seabed.

This isn't what gets Foley most excited about the project, however. His team will also dive around the entire island, a distance of about 17 nautical miles, using James Bond-style propellers to cover ground quickly. Foley hopes this could reveal a whole clutch of previously unknown wrecks.
The island of Antikythera sits in the middle of what has been a busy trade route since ancient times: a treacherous shard of rock notorious for downing ships in a storm. In Roman times, it was also an infamous centre for pirates. So it's a good bet that there are plenty of other wrecks here, from all periods of history.

On a two-day reconnaissance survey in June this year, Foley and his team discovered the wreck of a British warship called HMS Nautilus, lost in 1807, plus a range of ancient anchors, ceramics and a 19th-century naval gun.

This suggests the area hasn't been looted (which makes sense given the difficulty of diving here), so any new wrecks found could be pristine. "Everyone is very, very excited," Foley says of the upcoming mission. "This ought to be extraordinary."

He also points out that the Antikythera ship, with its valuable cargo, is unlikely to have been travelling alone. When it sank, others in its fleet may have gone down too. Could one of them have been carrying another Antikythera mechanism? For the past hundred years, this awe-inspiring device has stood alone, our only glimpse into a technology lost for millennia. That might – just might – now change.

Kathy Dowsett