Friday, November 30, 2012

History of the Dive Computer

In a 1951 secret meeting at the Scripps Institution of Oceanography in California, members of the US Navy Committee for Undersea Warfare and Underwater Swimmers discussed improvements to scuba diving gear. Top of their list was a foolproof way of monitoring nitrogen loading.

Two years later two Scripps researchers, Groves and Monk, published a paper that set out the functionalities needed for a decompression device. They said such a device must calculate three things – decompression during the dive, the remaining nitrogen in the human body from previous dives and, based on this information, an optimised, faster ascent rate. Groves and Monk suggested the use of an electrical analogue computer to measure both decompression and
air consumption.

American manufacturer Foxboro came up with the Decomputer Mark I in 1955 (above). It was the first analogue dive computer. A needle indicated danger during an ascent by moving towards a red zone on the display. After several test dives, the US Navy found the device to be too inconsistent – despite their efforts, the use of dive tables was still far more accurate.

It was back to the drawing board. In 1963 the SOS Poseidon 5 was introduced. It automatically calculated how long decompression stops should be based on dive depth and bottom time. However, imprecise calculations for deep and repetitive dives gave it the nickname ‘Bends-o-Matic’ and the US Navy advised against its use for recreational diving.

The same year the market saw the first electric analogue device – the TRACOR. The unit ran on two batteries, but the high power consumption, especially in cold waters, resulted in limited dive times and a worrying rate of system failure.

Next up was the MARK V S developed by the DCIEM (Defence and Civil Institute for Environmental Medicine). It was the first dive computer to tick all the boxes and was sold to industrial and military agencies in the 1960s but was not available to the public.

In the late 1970s dive computers went digital. The XDC-1 was a desktop device designed in 1979 for laboratory purposes and looked like a cash register. The device built the foundation for the improved XDC-2 and XDC-3, or CyberDiver that became the first digital portable computer and 700 units were sold between 1979 and 1982. The later XDC-4 worked with gas mixes, but was too expensive for the mass market.

In the 1980s the technology quickly improved. In 1983 the Orca Edge hit the market as the first commercially viable dive computer. The model was based on the US Navy dive tables but did not calculate a decompression plan. Its design was ahead of its time – it resembled an iPod Nano. However, production capacity was only one unit a day. It was never going to emulate Apple’s sales figures.

A year later, the Decobrain arrived and the modern recreational dive computer was born. It had all the features we have come to expect from a dive computer, including calculated ascent times and an integrated warning system for fast ascents. The Decobrain was also the first dive computer to achieve success in the European market.

DACOR’s follow-up model Microbrain was the first industrial scaled dive computer and the first one using a silicon chip.

In 1986 a little known Finnish company, Suunto, came out with the SME-ML. The computer had all the essential features and was able to store 10 hours of dives, which could be accessed any time. This, and the simple design, was key to its success and marked Suunto’s break into dive gear manufacturing. It took another decade before the Finns became market leaders.

In 1987 the Swiss company UWATEC introduced the Aladin that swept aside all rivals. The unattractive, chunky, grey housing could be seen strapped to wrists from the Red Sea to the Barrier Reef. Soon more divers were using computers than not – and more were using Aladins than anything else.

Thanks to Dive

Kathy Dowsett

Wednesday, November 28, 2012

5 Diving Tips for Saving Air

Diving Tips: Saving Air

Do you breathe your tank down faster than your buddy? Here are 5 diving tips to help conserve your oxygen and extend your bottom time.

1. Fix the small leaks

Even a tiny stream of bubbles from an O-ring or an inflator swivel adds up over 40 minutes, and may be a sign of more serious trouble ahead anyway. A mask that doesn't seal is another kind of leak in that you have to constantly blow air into it to clear out the water. It's also a source of stress, which needlessly elevates your breathing rate and thereby reduces your breathing efficiency. Does your octo free-flow easily? That can dump a lot of air quickly. Detune it or mount it carefully so the mouthpiece points downward.

2. Dive More

Inexperienced divers are famous for burning through their air supply at a furious rate, so one of the best diving tips for saving air is to simply dive more often. You may not be a new diver, but unless you dive almost every week it's still an unnatural activity. By diving more, your body will get used to the idea, and you'll breathe less.

3. Swim Slowly

The energy cost of speed is even more than you might think: Swim half as fast as you do now, and you'll use less air.

4. Stay Shallow

Because your regulator has to deliver air at the same pressure as the water, a lungful at 33 feet (two atmospheres) takes twice as much out of your tank as does the same breath at the surface. At 99 feet (four atmospheres) it takes twice as much as at 33 feet. There's absolutely nothing you can do about that except to avoid being deeper than you have to be. If you're making a transit over an uninteresting sand flat to get to the edge of the drop-off, do it at 15 feet instead of at 40 feet, and you'll save air.

5. Minimize the Lead

If you're overweighted, you have to put more air into your BC to float it and be neutral. The inflated BC is larger and requires more energy and oxygen to push it through the water. An extra eight pounds of lead means your BC is one gallon bigger when inflated enough to make you neutral.

Thanks to Scuba Diving----an informational scuba blog.

Kathy Dowsett

Sunday, November 11, 2012

Lessons for Life: Death in the Shallows

Thanks to Eric Douglas and Scuba Diving

Jolie kept hoping things would get better. She had been certified a year earlier, but had been in the water only once since then. Her first dive of the day had been shaky, but she got through it. She just couldn’t get the hang of her buoyancy, and felt like she was either banging off the bottom or floating to the surface. During the surface interval, her buddy told her she just needed practice and it would get better. She kept reminding herself to relax and breathe slowly and easily.

Visibility was poor on her second dive. She felt like she was looking down a tunnel and everything got dark. All she could think of was getting to the surface and breathing air. She was breathing faster and faster, but nothing seemed to be coming from the regulator. She spit it out and looked around wildly for her buddy.


In her mid-20s, Jolie was in good shape and enjoyed being outside. She thought learning to dive sounded like fun, and she enjoyed the classes. She dreamed of diving somewhere warm and sunny in clear water, but she hadn’t been able to make a trip to the ocean yet. Her friends went to a local quarry regularly, but Jolie never got used to it. She didn’t like the heavy wetsuits, and while everyone said visibility wasn’t bad, it made her feel uncomfortable and closed-in. She had had problems with claustrophobia when younger, and the dark water brought those feelings back.


Jolie was using some borrowed gear and had rented other pieces. She was reluctant to invest in equipment until she felt comfortable. When she got to the quarry, she realized that the low-pressure hose on her borrowed reg didn’t match the inflator connector on her rented BCD. She had learned how to orally inflate her BCD in her certification class, so her dive buddy convinced her to make the dives anyway. He reasoned that they were going to stay in the shallow end of the quarry where the open-water students practiced, a maximum depth of 10 feet. The one piece of equipment she forgot to bring was her weight belt. She ended up placing her weights in her BCD pockets.

Throughout the first dive, Jolie struggled with her buoyancy control. When she began letting air out of her BCD on the surface, she dropped quickly to the bottom. She orally inflated her BCD, and then found herself on the surface again. She felt like that was all she did the entire dive. She spent so much time working on her buoyancy that she never really looked around or had time to relax. The dive ended relatively quickly when she noticed she had breathed through her entire tank. Her buddy told her that was no problem, but asked her to try to relax and breathe more slowly on the second dive. He also told her to descend to the bottom and add in a little air into her BCD, not an entire breath every time.


Jolie’s panic began early in her -second dive. She was uncomfortable on the surface, trying to remember everything her buddy had told her and the lessons she had learned in class a year before. As soon as the water closed over her head, she began breathing quickly. Her buddy said later that it looked like a constant stream of air bubbles coming out of her regulator. She descended quickly and hit the rocky bottom on her knees. A group of students had just cleared the area and silt had been stirred up, reducing visibility to less than normal. Jolie stayed on her knees for a moment. She took the regulator out of her mouth and began scrambling for the disconnected inflator so she could add air into her BCD. She never found it. Her panic escalated. The only thought that reached her mind was that she needed to be on the -surface. Air.

Jolie’s buddy grabbed her alternate air-source regulator and tried to give it to her. When she refused it, he tried to give her his own, but she refused it as well. Without warning, she bolted for the surface. Resuscitation efforts on the beach and at a nearby hospital were unsuccessful.


This is a classic case of panic leading to a dive fatality. Jolie wasn’t thinking clearly in the water. She took out her regulator before she found her inflator hose. Just those few seconds without an air supply were enough to tip her over the edge.

There is very little you can do for someone in a panic state, aside from removing them from the situation and allowing them time to calm down. This is extremely difficult and dangerous underwater. But while the panic ultimately killed Jolie, the triggers on the dive caused the panic in the first place.

Jolie had latent problems with claustrophobia. Struggling with her buoyancy got her agitated to the point that she wasn’t thinking clearly. A root cause of this issue was the disconnected low-pressure inflator. She entered the water on the second dive with the same problems, now even more agitated.

An ascent from 10 feet was more than enough of a pressure change to cause a lung overexpansion injury and cause an arterial gas embolism, or AGE. This causes strokelike symptoms as a large air bubble is introduced to the brain, cutting off blood supply. It can also cause death rapidly. This is the reason scuba divers are trained to never hold their breath.

Lessons for Life

1 Don’t make dives you aren’t comfortable making. Don’t allow peer pressure to goad you into a dive you aren’t ready for.

2 If you feel panicked or have trouble catching your breath underwater, stop on the bottom or hold onto something stable and attempt to relax. Wait for your breathing to settle before you attempt to swim on. If that fails, abort the dive.

3 Be properly equipped for the dives you are making. Making do with improper equipment is unsafe.

4 Seek additional training and experience in a situation supervised by a dive instructor.

Eric Douglas co-authored the book Scuba Diving Safety, and has written a series of dive-adventure novels and short stories. Check out his website,

Kathy Dowsett

Tuesday, November 6, 2012

Eunice aphroditois aka 'bobbit worm'

Eunice aphroditois :: apparently given the nickname by an underwater photographer two decades ago.

It snares its prey using a complex feeding apparatus with two sharp mandibles which snap shut like a pair of scissors

The ocean floor is home to many weird and terrifying predators, many of which could discourage anyone from ever setting foot into the sea again.

This creature is Eunice aphroditois - also known as the Bobbit worm, apparently after an underwater photographer decided two decades ago that its hunting methods were similar to the Bobbitt family incident of 1993.

That incident involved Lorena Bobbitt slicing nearly half her husband's member off. E. aphroditois is similar, according to a 2011 paper in Revista de Biologia Tropical, 'because either the widely open jaw pieces resemble scissors, or because the exposed portion resembles an erect penis.'

The nickname is inaccurate - Mrs Bobbitt inflicted the grievous injury on her husband using a knife rather than scissors - but it has stuck nevertheless.

And it is perhaps a close enough comparison to dissuade any man from skinny dipping in warm waters near the sea floor at depths of 30 to 130ft, where the long-living nocturnal worm is generally found.

The creature, which spends its life mostly buried beneath the sand of the sea-floor, sticks just a portion of its body up into the water where it has five antennae to sense its prey, usually smaller worms and fish.

Mammoth: A scientists poses with the 10ft-long E. aphroditois discovered in Japan's Seto Fishing Harbour in 2009.

It snares its prey using a complex feeding apparatus called a pharynx which can turn inside-out, like the fingers of a glove, and has sharp mandibles on the end which snap shut like scissors.

Unlucky creatures are sometimes sliced in two because of the speed and strength of the worm's attacks, and it can dish out nasty bites to any humans who stray too close.

One the prey is caught, the worm shoots back into its burrow to feed. When prey is scarce it also feeds seaweed and other sea plants, and will scavenge for morsels around the surface of its burrow.

Noted for its unusually large body size and length, E. aphroditois is found in warm waters all over the world.

Since the 19th century, marine biologists have recognised it has having one of the longest bodies among polychaetes - a class of segmented, mostly marine worms.

They average a length of about one metre, but specimens measuring as long as three metres have been discovered.

The creature, which spends its life mostly buried beneath the sand of the sea-floor, sticks just a portion of its body up into the water where it has five antennae to sense its prey, usually smaller worms and fish.

It snares its prey using a complex feeding apparatus called a pharynx which can turn inside-out, like the fingers of a glove, and has sharp mandibles on the end which snap shut like scissors.

Unlucky creatures are sometimes sliced in two because of the speed and strength of the worm's attacks, and it can dish out nasty bites to any humans who stray too close.

One the prey is caught, the worm shoots back into its burrow to feed. When prey is scarce it also feeds seaweed and other sea plants, and will scavenge for morsels around the surface of its burrow.

Noted for its unusually large body size and length, E. aphroditois is found in warm waters all over the world.

Since the 19th century, marine biologists have recognised it has having one of the longest bodies among polychaetes - a class of segmented, mostly marine worms.

They average a length of about one metre, but specimens measuring as long as three metres have been discovered.

A report by Hiro'omi Uchida, assistant director of the Kushimoto Marine Park Centre in Japan, describes one such mammoth worm found hiding in one of the floats of a mooring raft in Japan's Seto Fishing Habour in 2009.

'[I]it is uncertain when the individual first entered the mooring raft and fish corral during the 13 years the structure sat in the harbour,' he writes.

'It is also uncertain whether the worm arrived by larval settlement or at a semi-adult stage of development. Nonetheless, the individual surely had been living in its comfortable floating home for a quite a long time.'

At 9ft 10in long, about a pound in weight and with 673 segments, the worm they discovered was one of the largest specimens of E. aphroditois ever found.

That same year, a report in MailOnline Science detailed how a 4ft-long specimen was unearthed in a Newquay, Cornwall aquarium that was attacking coral and prize fish.

Workers at the attraction had been left scratching their heads as to why the coral had been left devastated and - in some cases - cut in half. After staking out the display for several weeks, the last resort was to completely dismantle it, rock by rock.

Matt Slater, the aquarium's curator, said: 'Something was guzzling our reef but we had no idea what, we also found an injured Tang Fish so we laid traps but they got ripped apart in the night.

'That worm must have obliterated the traps. The bait was full of hooks which he must have just digested.'

Staff believe the beast - which they nicknamed Barry - arrived by hitching a ride into the aquarium hiding inside a piece of coral when it was young and grew enormous over a number of years.

Mr Slater added: 'It really does look like something out of a horror movie.

Thanks to the Daily Mail

Kathy Dowsett

Monday, November 5, 2012

Life on a "liveaboard"

It’s eating, breathing and sleeping scuba diving, 24/7.

That’s life on a “liveaboard” boat that Fraser Debney experienced in the Bahamas recently. He had liked his first liveaboard trip so he decided to try it again this year.

On April 13, Fraser and some of his friends left port in Nassau Bahamas aboard a Blackbeard Cruises ( liveaboard ship for a seven-day adventure. It would confirm his first impression of the experience. He loved it. The dive boat becomes your home and restaurant for a week and you don’t return to port until the trip is done.

“It would be our shark dive,” Fraser replies when asked for his favourite experience on the trip.

It takes place at a wreck site, and a good wreck dive on its own merits. But it is also a wreck dive with a difference. Using a rope, the boat’s crew suspends a glob of waste food about 20 feet above the divers. Looking up from the wreck the divers get a close-up look at the reef sharks, which range in size from four to six feet. Fraser acknowledges that many people object to attracting sharks like this but says it is good for tourism.

“These sharks were not aggressive and I don’t believe they generally are.”
That day they saw at least 20 sharks, as well as Nassau groupers and a lot of tropical fish, “all swimming around in the same area eating the scraps as the sharks chomped on the chum. Curiously, the sharks don’t bother them (the other fish).”

James Bond Grotto in the Bahamas, where the Thunderball movie was shot, was another favourite “because of the vast expanse of things to see. That movie is underwater battles. It is almost like a small cave. There were a couple of octopus, a lot of old and interesting elk horn coral growing out of the ground and various tropical fish that made the cave their own. It has an access and exit point.”

The boat itself is about 65 feet in length and on this trip accommodated 19 divers and a crew of six. Instead of cabins there are open bunk areas. Each serves as the sleeping quarters for four to six divers. “For anyone expecting 5-star it is not 5-star. It is camping on the water with the diving as a bonus. The diving is fantastic. As long as you are comfortable being in a trailer (atmosphere) and having to be organized, the space you have is adequate. If you spread your stuff all over it is not for you.

“All the entities of a dive shop are on the boat. You don’t touch your gear. They fill up the tanks on the spot. It was interesting for me,” says Fraser. “The food was fantastic. The meals were like homemade.”

Meanwhile, the boat is travelling from one dive site to another. While bad weather limited them to a couple of dives on the first two days, generally they made four or five dives a day. When moored at the end of the day they would do night dives before moving on to the next site in the morning.

The week-long experience costs $939. It includes everything to do with your diving, food and drinks, including a beer keg in the gallery, along with wine and rum punch.
“Your first alcoholic drink is your last dive (of the day). They’re very strict. If you have a drink at 10 a.m. you don’t dive at all.”

It’s not a loud and late night, either. Tired by the busy day of diving, most people are in bed by 8 p.m.

Kathy Dowsett

Saturday, November 3, 2012

Diving Doc: Preventing and Treating Coral Scrapes

Scuba diving is traditionally a look, don't touch kind of sport. But even careful divers can inadvertently run into trouble. By far the most common diving injury is the common scrape, usually from coral.

Irritations often occur as a result of a brush with coral or sponges. Coral scrapes can be painful and sometimes difficult to heal because the living organisms in the coral can get into the wound and cause infections. Contact with a sponge can leave irritating fibers in the skin, producing an itching rash that can range from mild to severe, possibly with pain and blistering.

Even if you're careful, it's likely you'll come into contact with coral someday. If and when, here's what to do:

1. An ounce of prevention is worth a pound of cure. Makes sure your body is covered, even if just by a dive skin, and wear gloves where allowed.

2. Regularly irrigate a scrape with copious amounts of vinegar over a period of about 30 minutes.

3. Apply triple-antibiotic to the wound twice a day for a couple of days.

4. Scrapes can become infected even with proper initial care. Watch for hotness to the touch, redness or red streaks around the site, swelling, discharge of pus, or fever. If you see them, contact a doctor.

5. Fragments of coral sometimes become lodged beneath the skin and the body mounts a prolonged allergic reaction to them. In some cases, debridement is required to resolve the reaction.

Even in the absence of embedded coral remnants, it is not unusual for a marked hypersensitivity response to a coral injury to continue for three to four weeks before significantly improving. Sometimes the lesion will resolve, then return.

If a scrape doesn't substantially resolve within a month, or gets worse, you should consult a dermatologist.

Editor's Note: Even innocent injuries can turn deadly if you have an allergic or severe reaction. After any accident, watch for severe swelling, dizziness, blurred vision, breathing difficulties, weakness, muscle pain, cold sweat and a rapid heartbeat. If any occur, call 911 (or DAN's emergency hotline 919-684-4DAN if no emergency services are available) immediately. Injectible epinephrine can help calm allergic reactions. CPR may be necessary until help arrives.

DocVikingo has been scuba certified for more than 35 years and has dived all over the world. He is a practising doctor in the Baltimore/Washington D.C. area and has held faculty positions at several major hospitals, including Johns Hopkins. With an interest in diving medicine, he serves as administrator at Scuba Clinic Online.

Kathy Dowsett