Decompression Dive Training Environments – Cave vs. Ocean vs. Inland

While some may think that decompression training is the same regardless of where the dives are conducted, that isn’t the case. It’s true that the theory is much the same. Advanced Nitrox/Decompression Procedures introduces divers to the basic principles of decompression. Basic (Normoxic) Trimix introduces divers to the basic principles of diving while breathing helium. And Advanced Trimix expands on these basic principles and prepares divers to go to deeper depths. There are different decompression models available for use. There are different methods of determining Equivalent Narcosis Depth. The physiology is the same. However, dive planning and execution can be quite varied dependent on where the dives are to take place.

Unless a diver is planning on “flying the computer”, something I don’t subscribe to, conducting decompression dives in a cave environment requires knowledge of the profile of the cave. It’s not as simple as descending to the maximum depth, staying at that depth for a designated period of time, then beginning the ascent with the planned decompression schedule. The hard floor and ceiling of the cave often dictates the dive profile. A direct descent and ascent may not be possible. There may be an extended period of time during the decompression schedule where you must stay at a specified depth because the ceiling prevents you from making an ascent. Sometimes the ceiling may even require you to descend 10-20 ffw after you have already started your decompression schedule! Planning decompression dives in a cave environment requires quite a bit of attention to detail. Respiratory minute volume must be known otherwise you may not even have enough gas to get to your planned destination. Swim pace must be known otherwise you may not get to your planned destination in the time you allotted. It’s not as simple the square profile diving typically done in ocean and inland bodies of open water.

However, in the ocean, there are other considerations that must be accounted for. While planning the dive may not be as involved as for a cave dive, environmental factors must be considered. What are ocean conditions like? Is the surface choppy, making entry into and exit from the water an issue? Is there a current that could blow you off the line and/or the dive site. Will the dive boat tie into the dive site or do a live drop and pick up? The dive can be done as a square profile, which is fairly easy to plan. However, the decompression portion of the dive my require a jon line to hang comfortably off the line, or a surface marker buoy to mark your location as you do a drifting decompression. Also, unlike in cave diving, you must keep your decompression cylinders with you rather than being able to drop them off at the beginning of your dive. While it’s always a good thing to be familiar with respiratory minute volume so that you know if you have enough gas to stay down for your planned time, it may not be necessary to effectively execute the dive. Once you get to your turn pressure, you simply being your ascent. There is no hard ceiling to prevent this. Also, if something goes wrong during the dive causing you to have to abort early, you can simply begin your ascent. In a cave environment, you must make your way back to open water before you can begin your ascent. None of these issues is seen in inland bodies of water.

Inland bodies of water, such as lakes (with the exception of the Great Lakes), quarries, and sink holes, are fairly neutral environments. While there may be entanglement hazards, there are typically no currents, no rough surface conditions, no drifting decompression stops, no hard overheads. Dive planning involves planning for a square profile, heading out to the dive site, and executing the dive. Surface marker buoys will be deployed because all agencies require this skill, but it’s not necessary for the dive, just for the standards. The biggest issue with inland bodies of water is the decreased visibility, which actually makes the instructor’s job much more difficult because it’s not as easy to keep track of all the students. For the student, it’s an easy environment.

So where should decompression dive training take place? While the initial dives should take place in a neutral environment to introduce skills and ensure students are able to perform the skills, final dives during the various courses should be conducted in the environment the student will be doing most or all of their diving once training is completed. If the student will be diving in both cave and ocean environments, then dives should be conducted in both. However, to take a student through this type of training and only conduct the training dives in neutral inland environments is only doing a disservice to them. Remember, training prepares divers to dive in similar conditions as what they experienced during their courses. Therefore, training in a lake or quarry does not prepare a diver to dive in a cave or the ocean. When you prepare to do your decompression dive training, make sure your instructor is going to take you to dive sites that are similar to where you plan on diving. If you have to travel for your training, then do so. Don’t settle for mediocre training in a lake or quarry.

Make sure you visit Chipola Divers and check out the Decompression Dive courses we offer. Our courses are conducted in caves for cave trained and certified divers and/or on the Oriskany or in South Florida.

Oriskany diving off the M/V Spree with Joel of TDL

I’ve wanted to dive the Oriskany since it was put to its final resting place in May 2006. Even after living in the Florida panhandle for 3.5 years, I still hadn’t made it out there. There were a couple of reasons for that. First, not many charters will cater to divers who want to do decompression dives on the Oriskany and allow them to do the diving they want to do. Second, spending a couple of hours on a small boat to travel the 20+ miles off shore, followed by another couple of hours to get back to shore isn’t appealing, especially when only one decompression dive is allowed.

A few months ago I came across information about a liveaboard experience out on the Oriskany. The trip involved heading to the wreck, tying onto it, and staying put for 3 days of diving. And to make it even better, it was a trip catering to decompression diving. Joel Silverstein, Tech Diving Limited, was the trip organizer, and knowing about his previous trips, I knew this would be a great trip. After a couple of e-mails with some questions I had about the trip, I was booked.

October 6^th arrived and I was packed and ready to go. I left for Pensacola in the afternoon, arriving at Joe Patti’s around 5pm. Several divers were already there and loaded. I loaded about 500 lbs of gear onto the M/V Spree, the boat we would be living on for the next 3 days and 3 nights. If I could have driven my van onto the sun deck, I would have!

Here’s one of the nice things about the Spree. It can sleep 24 people in the main passenger cabin, but since we were a technical charter, there were only 12 divers on the trip. We had more tanks and more gear and needed more space, and we are willing to pay for that extra space. We had plenty of room for everything we brought with us. The Spree also has banks of air, nitrox, oxygen, and trimix. She also has a booster onboard so O2 cylinders could be topped off properly.

Once settled in, we headed into the Salon for the boat briefing. Captain Frank Wasson, owner and captain of the M/V Spree, is quite the character. I realize he’s done this briefing hundreds of times, but he still keeps it interesting and funny, using visual aids and more! I won’t reveal any information from the briefing, but let’s just say I had nightmares about the toilets! :D For anyone who’s been on a boat with plumbing, you know there are certain things you need to do to keep them functioning…especially with 12 divers who are consuming every last bite of food on board!

After the briefing, we hung out for a while talking and getting to know each other before turning in for the night. The Spree wasn’t due to leave dock until 4am, which was nice since the tide would be in our favor. We finally headed off to our bunks eagerly anticipating waking up floating over top of the Oriskany.

Most of us were up before 7 and watched the activities on deck as the crew was getting ready to set its mooring line. It went without a hitch. The Spree crew had already set the chain on the flight deck less than 50’ aft of the island on a previous trip and just had to tie in to it. The depth at the chain was about 150 fsw. We had breakfast and prepared to splash by 9am. The night before we had discussed the plans for the trip and decided a maximum of 2 dives each day would be the rule due to the depths we would be going to. Everyone was fine with that. In fact, some days some divers only did 1 dive.

While on this trip, I did 2 dives a day for a total of 6 dives. My maximum depths for those dives ranged from 149 fsw to greater than 200 fsw a couple of times during a visit to the screws and to the bow of the wreck. Most of the dives stayed in the 130-170 fsw depth range. Everyone on the trip came with a buddy and I was going to be diving with Joel most of the trip. Not only was I there to dive the Oriskany, but I was also working on my Advanced Trimix Instructor rating with Joel. Joel has done a lot in the dive industry, and specifically in decompression diving. He’s worked with some of the best minds in the industry and published lots of papers on decompression theory. I couldn’t think of many others I could learn as much or more from. I got a lot of information during the trip and a lot of great files from Joel, some of which I will be incorporating into my own courses.

The first day was used for orientation dives. Most of us dropped down the line and headed over to the island, the only interesting attraction above the flight deck. The island sits just aft of center on the starboard side of the Oriskany. The flight deck is at 150 fsw with the top of the island in the 90 fsw depth range. It may be a little shallower, but during our island dive we swam around it checking out all of the features and didn’t see anything that was much of interested shallower than 90 fsw. A couple of dives on the island and we saw all of the outer parts of it and even did some minor penetrations.

The second day we took the scooters and headed back to the stern to check out the screws. We dropped down to the flight deck, over the starboard side of the wreck to about 180 fsw and scootered along at that depth checking out the various openings to the wreck, including the openings to the hangar deck on both sides. At the stern we dropped down and swam over to one of the screws that was about as big as a Volkswagon Bug! After a few minutes we headed back up to 180 fsw and scootered along the port side of the wreck until we got back to the area of the island and ascended up to the flight deck to cut back across to our mooring line for our ascent. After our decompression, we got back on the Spree to have lunch. Three hours later we splashed again for a shallower dive around the island.

Our third day we planned a penetration into the Hangar deck. We dropped down the mooring line, headed over the starboard side just over one of the Hangar deck entrances and set a line. While the opening to the Hangar deck is pretty large, the visibility wasn’t good enough for us to see light all the way across the deck. We reeled all the way across to the other side and tied off at the top of a ladder that led to a lower deck which is located pretty close to an outer door. The dive was turned on gas and we headed back to the mooring line for our ascent.

The final dive of the trip was scooter time again! After gearing up and splashing, I hit the trigger and dropped to the flight deck in about a minute. Once at the flight deck, I checked my watch and kicked the speed up to speed 3 on my SS Magnus. I headed to the bow about 10’ off the starboard side of the flight deck, dropping down at the bow to check it out for about a minute, then back up to the flight deck continuing back along the port side, rounding the stern and back to the starboard side until I reached the mooring line again. The Oriskany is 911’ long and about 150’ wide. Add some additional distance to make up for staying about 10’ off the edge and that puts this trip at over 2200’, which I was able to complete in less than 10 minutes, including the time spent checking out the bow. And, the current had kicked up to probably its worse the entire trip! Once returning to the mooring line, I headed over to the island and scootered around it a few times to see if I missed anything on my previous dives. I still had time to pass until my planned ascent, so I scootered along the flight deck, zig zagging all over the place until I got bored and decided to head back up.

During all the dives, bottom temperature was 68 degrees (just my temp!) with visibility ranging from 30’ to about 90’ at its best. The best conditions we had happened on the first day. There was a significant thermocline at 110 fsw dropping the temperature from 79 degrees to about 70, followed by another slight thermocline at about 130 fsw. The current was fairly significant the first dive of the trip and almost nonexistent the second dive of day 1. It then kicked back up days 2 and 3, being the worse the afternoon of day 3. It was going starboard to port the entire time.

We couldn’t have planned for better weather. It was sunny and in the 80s the entire time we were there. Capt. Frank likes to keep the inside of the Spree fairly cool. Some of us were wearing sweatshirts when inside! The seas were less than 3’ the entire time. And we got all of the dives we wanted! The service on the Spree is top notch! Capt. Frank and his wife, Mel, run a great ship and service. The food was great, and the chefs were able to accommodate my request for vegetarian food. Everyone on the crew was courteous, friendly, and helpful.

The Oriskany is definitely a great dive site for divers able to go beyond recreational depths and spend some time at depth. While there are some things to see on the island, its depth doesn’t allow for much bottom time for divers unable to stay beyond no decompression limits. It’s definitely better suited to divers able to plan and execute decompression dives. It’s somewhere I would definitely like to use to train students in Advanced Nitrox/Decompression Procedures and Trimix if I can find a charter willing to work with the schedule I need. In the meantime, I know the Spree will be heading back there for more extended trips and I plan on taking advantage of that.

All in all, it was a great 3 days of diving with a great group of people. I got to meet some people I have only known through the Internet and spend some time learning from Joel, who I’ve known for several years now. This was my first “technical” liveaboard, but will definitely not be my last.

Oh, one more thing, I finally got to do my first sidemount dives off a boat. Here’s my assessment – it’s so much easier than backmount! At least on the Spree, it was. The benches are tall enough on the Spree that I was able to clip my cylinders on while the bottom of the cylinders rested on the bench. Once my sidemount cylinders and decompression cylinders were all clipped on I made my way to the starboard side to splash. I quickly put my fins on and did a giant stride off the side of the Spree. At the end of the dive, getting out of the boat was also not a problem. The first day, I did my dives in backmounted 95s and had a difficult time climbing the ladder back onto the Spree. Climbing the ladder was much easier in sidemounted 108s, even though they are heavier. The location of the weight makes a huge difference in how it feels on your knees and ankles coming up those ladders and on your center of gravity. With sidemounted cylinders, you are being pulled down, not backwards. Granted, we were only in 2-3’ seas, but it was definitely easier for me. Unless I’m teaching divers in backmount, I will definitely dive sidemount off dive boats!

Don't forget to visit our website - Chipola Divers!