Deco dummy here - I really have no clue what the deal is...

[Northeastwrecks]

The dive you've proposed would be a trimix dive that is beyond my current limits. While my planner would do it, I don't feel entirely comfortable with the calculations.

I do, however, do shallower (less than 150 fsw) deco dives.

I don't find deco hangs particularly confining or troubling. I view them as the price of the deeper dive.

The reason I dive deeper is four fold. First, the excitement of going where very few people have gone before and seeing things that are otherwise inaccessible. Some of the wrecks are literally pieces of history. To see and touch the deck of a wreck is an incredible feeling.

Second, the comeraderie of my dive buddies is great. We are all great friends.

Third, the challenge of properly planning and executing the dive is a good rush.

It is true that, with one exception, most of the depths I dive could be done as non-deco dives. However, what would be the point of a 3 minute touch dive. Deco diving allows you more time to explore.

 

[SDAnderson]

DON'T TRY THIS WITHOUT DECOMPRESSION DIVING TRAINING

This is very complicated stuff and if you make even a small mistake you can be seriously hurt or killed. It's a miserable, painful and ugly death.

In addition to time and depth, there are a lot of variables that affect the answer you are looking for. Gas mixes, decompression models, ascent rates, deep stops, water temps, stress levels, etc., etc., will all influence these calculations. There is too much art and not enough science to this, thus the ongoing debates.

Given that there can be multiple workable methods, here's one possible result:

You'll start your dive with two tanks filled with 21/38 trimix, plus one tank of EAN50 and one tank of pure Oxygen to use as decompression gases. Dive to 175 feet. Including descent time, you spend 25 minutes on the bottom. It's going to take you 45 more minutes to get back to the surface, including 10 decompression stops, for a total run time of 70 minutes.

Change the depth from 175 to 250 feet and the calculations change dramatically. The first big difference is that you have to change to a hypoxic trimix, lest the normal 21% oxygen cause convulsions and drowning at depth. You won't be able to breath the trimix at the surface, however, since the low oxygen level might cause you to pass out. You'll still need the same deco gases, but you'll probably have to switch to bigger tanks to hold enough gas. It's a problem if you have to choose between the bends and drowning. Dive to 250 feet. Including descent time, you spend 25 minutes on the bottom. It's going to take you 128 more minutes to get back to the surface, including 16 deco stops, for a total run time of 153 minutes. This dive will definitely give your skin the prunies.

Is it worth it? Depends. I'm a destination (as opposed to process) driven diver, so there needs to be something down there worth seeing. Given that the flora and fauna start to thin out as the depth increases, most of the really deep destinations are wrecks or geologic formations. They can be really cool, but there's a lot of cool stuff to see at 60 feet and most divers are happy with recreational limits, including me, most of the time. Long decompressions on a warm reef are fine with me - I like just hanging around watching the fishies. Hanging in open water is another story, however. You hope and pray for a decompression so boring (is that a shark in the distance?) that you and your buddies can take turns reading a book.

Don't forget - get the training before you try this. Even with the training, you can still get badly hurt, without it you're just asking for death.

Hope this answers your question.

Steven

 

[Mo2vation]

wow...where to start. Thanks Steven. Thanks Aquatec.

First, I am surely about the destination, and not the journey - in every other aspect of my life. My wife and dive partner is the complete opposite. She loves the drive, I nod off and can't wait for the destination.

In diving, I guess I'm different that way. I'm still in that wanderlust stage of rubberneck gawking - the "look at that...OOOHHH look at THAT" kind of thing...

We did my deep dive for my AOW at San Clemente Island in CA, at a place called "the Arch". PLanned to go to about 102 fsw. Current was ripping, so it was down the rope go thru the arch a time or two, then back up. My instructor was very cautious with all of us (which, of course, I appreciate) but it was what I would consider a total "touch dive"...

I had a good EAN mix and had more bottom time in the bottle, and emerged with lots of gas left. I was a little miffed. I really enjoyed the journey - all the bubbles, the open ocean, the excitement of going that deep, the WOW of seeing the arch ermerge from the blue water, oozing and fizzing with thousands of tiny bubbles filtering through the top of it...it was amazing.

The destination part of the trip was cool - the arch was wonderful, but the journey was the best part of that dive for me.

There is surely a ton of training and research involved in deco diving. Your description of the contrast between a cold, open water hang vs. a warm warter reef hang, and the time commitments involved with this type of diving really helped.

I need to a lot more dives under my (weight) belt before I consider this 'other' type of diving. Its going to be a while before I can consider this. Thanks everyone.

Ken

 

[tinman]

MO: Get "THE LAST DIVE". It is a great read for those trying to understand deep dives, motivation to dive deep, and the dangers of the deep. Many lessons found in those pages can apply to recreational depth diving...