I received my first "C" card after completing the 8 week diving phase of training in Basic Underwater Demolition and SEAL (BUD/S) Training at USNAB Coronado, CA in '79. We spent our first 3 weeks doing "standard" Open-Circuit SCUBA training with twin-72 cu.ft. steel tanks in the pool, in San Diego Bay, and in open ocean. "Standard" training included underwater equipment disorientation drills (our instructors were most helpful at this!), high-surf ocean beach entry and exits, 1 mile underwater compass swims, and "jock-up drills" (pushups with 80 lbs worth of dive gear on our backs) when we screwed up. We tried not to screw up a lot! |
We spent the next two weeks diving with an old WWII closed-circuit oxygen rebreather rig called an Emerson. It had a pair of vest-mounted rubberized canvas "breathing bags", and a fiberglass backpack which contained a small oxygen (O2) cylinder and a carbon dioxide (CO2) scrubber canister. A needle valve could be adjusted to meter O2 appropriately for your breathing rate, and a "dump" valve was used to add large volumes of O2 to maintain your breathing volume any time you descended. You could swim underwater at shallow depths with this for over 6 hours, without giving off any bubbles! While diving the Emerson, we got to perfect our night underwater compass swims and swimmer-ship sneak attacks.
The Emerson did have a few disadvantages. First, because 100% O2 becomes toxic to the human body at pressures much above 1 atmosphere, we were limited to shallow depths, and could only briefly dive deeper in case of emergencies. Second, the Emersons were old, and sometimes developed leaks. When water got into the rebreather loop it mixed with the chemical granules in the CO2 scrubber canister and made a "caustic cocktail", which you inhaled on your next breath. Imagine trying to gargle a mouthfull of seawater and Drain-O at 20 feet without any "air".
Our last 3 weeks of dive phase training was spent with the Mark 15, a $25,000 fully-computerized state-of-the-art rebreather. It had an O2 bottle, a diluent gas bottle, the CO2 scrubber cannister, and a flexible diaphragm breathing expansion chamber with 3 O2 sensors and a computer all fully contained in a fiberglass backpack. The 3 O2 sensors monitored the partial pressure of O2 in your breathing mixture, and the computer would continually maintain 0.3 atmospheres partial pressure of O2 in your breathing gas mixture, which allowed you to dive at any depth without succumbing to oxygen toxicity. As you dove deeper, the rebreather diaphragm activated a valve that added diluent gas to maintain the volume of your breathing mixture.
The diluent gas could be either nitrogen (N2) or helium (He), depending on the depth requirements for the dive. Because the Mark 15 always maintaned your partial pressure of O2 at 0.3 atmospheres at any depth, the remainder of your breathing mixture was the diluent gas. When using N2 for the diluent, your risk of nitrogen narcosis or getting the bends was greater using the Mark 15 than it would be using conventional open circuit SCUBA. For example, I remember doing one open ocean (there wasn't a bottom) 120 foot "bounce dive" for training with the Mark 15. At 120 feet I was breathing a mixture of 0.3 atmospheres O2 and 4.7 atmospheres N2 (only 6% O2 and 94% N2!) For nitrogen saturation, this was like diving open circuit SCUBA at 150 feet. I remember definitely being "Narc'd", and then having to do a couple of significant decompression stops.
After all this, they gave me a NAUI Open Water I "C" card. I don't know, is PADI certification any easier?
Here are a couple of pictures of Barb and Kristin from our second dive trip, to Grand Cayman Island. Here's one of me at Stingray City Sandbar feeding the stingrays. The rays are really very tame. They have incredibly soft silky-smooth underbellys, and are a lot of fun to pet. We fed them by holding small pieces of squid in our fist, which the rays quickly "sniffed" out. They can generate a pretty good vacuum with their mouths and can suck the food right out of your hand. They are a lot like an underwater Hoover!
Barb and I took our third trip together in March '97 to Bonaire (part of the Dutch West Indies located 50 miles north of the coast of Venezuela) this past March. We went with a really fun group of people from The SCUBA Diving Company, stayed at Captain Don's Dive Habitat, and had a terrific time the whole time we were there. We saw lots of colorful sponges, LOTS of fish, several 6' to 8' green moray eels, and dove a wreck called the Hilma Hooker. I'll try to get some pictures scanned in some time soon!
Our most recent dive trip was to Roatan, a small island north of the coast of Honduras, in January '98. We stayed at Anthony's Key Resort, on a smaller island (key) next to Roatan. AKR was a wonderful place to stay, with a very relaxing atmosphere. Right next to AKR is the Roatan Institute of Marine Science, which has a terrific dolphin and marine science program. Here is a picture of Barb playing in the dolphin pen.
Rodale's Scuba Diving Magazine.
Last Updated: November 15, 1998