Drift Decompression Diving

by David Miner

Diver deploying a lift bag on a free ascent decompression drift dive

Standard drift diving is a specialized form of boat diving allowing you to drift with the underwater currents during your entire dive. The boat is never anchored or moored and follows the group of divers the entire time. The different types of drift diving are: float drift and live boat drift. Float drift diving involves the use of a float with a down line or drift line that is towed by the dive leader or divemaster and always lets the boat captain know where the group is. The boat captain follows the float on the surface. Live boat drift diving requires no drift line forcing the boat captain and crew to follow the divers’ bubbles as they drift along.

However, there are also sometimes strong currents on deeper wrecks or other dive sites where you don’t want to drift during the dive, but must drift during your decompression stops on the way to the surface. There are several forms of drift decompressing after the dive is complete, anchor line drift decompressing, float/buoy line decompressing, and free ascent decompressing. Whether drifting for the entire dive or diving a wreck and only drifting while decompressing, there are things to consider and special equipment needed to safely complete your decompressions stops and surface with the boat waiting to pick you up.

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Treatment of Decompression Illness

If DCI does happen, proper treatment is very important. First aid for DCI is immediate administration of 100% oxygen either through a demand mask that cover’s the patient’s face and delivers oxygen when the patient breathes. If the patient cannot tolerate a demand mask, a nonbreatheable, free-flow mask can be used with a flow rate set to 15 liters per minute. Masks should seal to the patients face so that maximum O2 is delivered to the patient. Air leaks in the mask will dilute the O2 percentage inspired. Do not use less than 100% oxygen as a way to prolong oxygen supply. Divers Alert Network (DAN) offers a variety of oxygen kits for the diving community as well as training in their use.

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Ice Diving Training

Ice diving is cutting a hole in the ice on a lake or other body of water and descending below the ice. There is a good bit to learn before you should start ice diving. A good team that is knowledgeable about every aspect about ice diving is important. There is some special gear and procedures that must be practiced before ice diving. Getting the proper training before you decide to ice dive is essential.

Some training agencies offer ice diving training, such as NAUI and PADI. Ice diving training includes planning, organization, techniques, and potential problems as well as site selection, preparation, special equipment, and safety diver procedures. Contact your instructor or training agency to determine exactly what they offer.

The Five Rules for Safe Cave Diving

Cave diving has been taking place since the 1960s, and unfortunately, there were some accidents. But, after reviewing many of the accidents, cave diving instructors and explorers, like Sheck Exley, determined that many of the accidents had resulted from the same mistakes. As a result, the following five rules for safe cave diving were developed.

Proper training and not exceeding your skill level and limits is the primary reason for cave diving accidents. Many of the cave diving fatalities over the years have been because the diver wasn’t cave certified or was trying to do a dive that was well beyond his/her abilities. Without the proper training, cave diving can be an extremely dangerous sport. Cave diving requires a special mindset, special techniques and equipment, and procedures that you can only get in specialized cave and cavern diving courses. No amount of experience, number of dives, or open water certification level is enough to safely cave dive; you must participate in cavern and cave diving courses to conduct safe cave dives.

Use a continuous guideline from the entrance of the cave and throughout the dive. Without a continuous line, you’re relying on memory to find your way out of a cave. Caves do not look the same on the way out as they did on the way in. Visibility can change, silt outs can occur, lights can fail, which all can contribute to getting hopelessly lost. A guideline to the cave’s exit is basically a lifeline; it’s the route out. Always run a continuous line from the entrance of the cave and throughout your dive. Don’t make jumps without running a gap line. Don’t assume that since you’ve dove the cave before that you don’t need to run a line from the entrance, things can change from dive to dive.

Always reserve at least two-thirds of your beginning gas supply for exiting the cave. This is also known as the Thirds Rule. Exhausting more than one-third of your gas supply for the swim into a cave does not allow for adequate reserve amounts. If you use one-third to go in, you’ll need one-third to exit and will have one-third for emergencies. The thirds rule is also extremely important in buddy teams. If a team member had a catastrophic gas loss at maximum penetration and had to rely on their buddy’s gas supply to exit the cave, the two-thirds of remaining gas would be required to get both divers out of the cave safely. Cave environments are not all the same, meaning that the thirds rule may have to be altered. If you’re diving in a siphon system, swimming out of the cave against the flow may require more than one-third of your gas supply, meaning that you may not want to go until you’ve used up one-third of your gas. Other adverse conditions may require a more conservative gas planning strategy as well. Each cave dive requires specific gas planning. Don’t just assume that the Thirds Rule applies everywhere.

Limit your dives to the operational limits of compressed air (130 fsw). Diving below 130 fsw on standard air increases the risks of nitrogen narcosis and the deeper you go increases your chances of getting oxygen toxicity. With the modern day advances and applications of mixed gas diving, there is no reason to dive deep on air. Trimix training is available through many of the training agencies. Mixed gas diving reduces nitrogen narcosis and oxygen toxicity, which in turns drastically increases the safety of a dive. If you can’t afford to get trimix certified or purchase the helium needed to conduct a dive, then limit your dives to recreational limitations of 130 fsw.

Always carry at least three battery powered lights on every cave dive. On a cavern dive, where the natural light acts as a third light, you only need to carry two battery powered lights. Lights are sometimes the most vulnerable pieces of dive equipment, meaning that they can fail easily. Bulbs can blow, wiring can fail, and batteries can fail. By carrying at least three backup lights, the likely hood of all three lights failing on the same dive are slim. In addition to just carrying the lights, you need to make sure you take care of your lights. Change your batteries frequently and make sure rechargeable lights are charged prior to the dive. If you have a lot of hours on a bulb, you may want to replace it before it fails. Without proper and reliable lighting, cave diving can be a very dark sport.