Max Depth for CESA

[dumpsterDiver]

A free ascent (from 60) with the regulator out was required when I got certified. We didn't have BC's or pressure guages and at the bottom of a quarry a 1/4" suit is pretty compressed.

I remember I took the reg out and started swimming up, the vis was about 5-8 and the temp was 40.... After a short while of swimming and exhaling I began to get a little tired and i didn't notice the water getting any brighter. I looked down and I was just 5 feet off the bottom, essentially treading water and fighting negative buoyancy (making zero progress toward the surface) and was about out of air. I was near panic by this time and just bolted for the surfce as fast as I could. I made it, but it was not easy. My dad said I looked less scared than some of the other students when I reached the top.. I was 13.

 

[Mr Carcharodon]

What is the maximum depth that one can do a CESA ?



- Bill

It seems to me in my LA County class we CESAed from 50 feet and I am told UICC did from 100 feet in the past. They did build up to that and did the deep CESA at the start of a dive. So 100 feet is viable, but as others have said its better to focus elsewhere. Repetitive quick ascent done in training are a good way to feel really bad, but that beats drowning.

 

[TSandM]

The "C" in CESA stands for "controlled" . . . that means it isn't a "blow and go". The emergency buoyant ascent is also discussed, but is a less desirable option. ANY option is better than staying underwater to drown.

A CESA is actually not terribly difficult from 40 feet or so, although the way we set them up in class is very artificial, because the students can hyperventilate before starting up (which you aren't going to get to do, if you are suddenly out of gas) and they start them with full lungs, which is an unlikely condition to precede a CESA.

If you are much deeper, you are looking at a strong desire to ascend at a faster rate -- which is better than drowning, but does raise your DCS risk. The OP is completely correct in thinking that the most likely times to be out of gas are at the beginning of the dive (tank turned off) and at the end (didn't monitor gas). In the former circumstance, you are not only doing a CESA, but you are having to swim up a negative diver/rig system, so you are working harder, using oxygen faster, and generating more CO2. That's all bad. At the end of the dive, you at least are likely to have SOME gas in your BC, which will help you with the ascent.

 

[261311]

While that's true, I thought the major difference between CESA and EBA was dropping weight and consequently having little to no control over your ascent rate? That's at least how it was described to me, it seems like I couldn't "swim fast enough" for my instructors preference during our training.

 

[supergaijin]

Bret Gilliam was involved in a shark attack which saw him doing a 'somewhat' buoyant ascent from very very deep. It was the early 70s and depths must be estimated but he was OOA at over 300ft.

Shark Attack! | Divers' BlogsThe previous deepest depth that a diver survived a
free ascent from was 180 feet. Gilliam was probably closer to 400
feet.

 

[TSandM]

I guess the point I was trying to make is that the idea behind a CESA is that the ascent rate is not "as fast as you can get to the surface", but a controlled ascent rate. A controlled rate would generally be at the maximum accepted ascent speed, which is 60 fpm; if you have to go faster than that, you are outside the boundaries of any decompression model -- but that is still preferable to drowning. I think most divers would be surprised to learn how fast 60 fpm is -- even 30 fpm feels awfully fast. But at 60 fpm, you are still looking at more than two minutes to get up from the bottom of recreational depths, and two minutes is a LONG time to go without breathing -- try it!

But this thread is doing what all CESA threads do -- and what John Chatterton was trying to warn against in his recent "Accomplished Bad Divers" blog post. We are arguing about the details of a salvage procedure which should NEVER be necessary. If you plan your dive and your gas, and you stay with a buddy who has done the same, the only way you are going to run out of gas is if you have a catastrophic gear failure, and in that event, your buddy is at your side with enough gas to get both of you to the surface. To need to CESA, you have either to fail to plan your gas, or fail to monitor your gas, AND lose your buddy. It's so preventable -- rather than argue about how to do it, why don't we talk about how NOT to?

 

[dumpsterDiver]

While that's true, I thought the major difference between CESA and EBA was dropping weight and consequently having little to no control over your ascent rate? That's at least how it was described to me, it seems like I couldn't "swim fast enough" for my instructors preference during our training.

Why would dropping lead necessarily cause an uncontrolled ascent?

 

[TSandM]

DD, if you're diving wet in Florida, it might not.

If I drop the 20 lbs of lead I wear around my waist in Puget Sound, I seriously doubt I'll be able to control my ascent, once I get into the shallows. I would be surprised to learn I can swim down 20 lbs of buoyancy.

 

[dumpsterDiver]

This shows an ascent of 200 feet in 25 seconds..I'm not sure what deco model they use for this.

http://www.scubaboard.com/forums/ad.../447870-video-ascent-200-feet-25-seconds.html

---------- Post added March 22nd, 2013 at 11:24 PM ----------

DD, if you're diving wet in Florida, it might not.

If I drop the 20 lbs of lead I wear around my waist in Puget Sound, I seriously doubt I'll be able to control my ascent, once I get into the shallows. I would be surprised to learn I can swim down 20 lbs of buoyancy.

Sure dropping 20 lbs will make you buoyant, but the amount of weight was never specfied in his statement.

Have you ever removed a weight belt at depth when wearing a wetsuit? We were diving in the springs one time with like 12-15 lbs of lead, we got to 80 feet or so and laid the belts out on the bottom, vented the BC's and were perfectly weighted. Boy i was pissed when we got back and two kids had stolen both belts from where they were placed...LOL

We hurried to the surface and demanded that these kids open the trunk of their car...they BARELY escaped a beating!

 

[Sam Miller III]

LA Co Basic diver 33 feet


LA Co UW Instructor 66 feet and 99 (100) feet


George Bond, USN, 302 feet, submarine

Dick Bonin, USN, ( founder of SCUBA Pro) 200 feet- In cold water reg mal function

Me? 100 many times..120 deepest..entanglement in life bag

When you are out of air- controlled or uncontrolled - it is blow and go, flare and you're there!

SDM