Request for accuracy for a film...

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They can hit the surface in about a minute with the ascent bag pulling them up. It might be wise to make a harness, as the rope will be pulling very hard on the way up, especially with the drag of a DIY dry suit...
They could, but should not really need to....the problem with sipping is getting to the bag, unless you started almost physically inside it--meaning zero control or visual to navigate around submersible or any other structure involved at depth. Remember, with a large enough bag, you are at the surface in about a minute. Not that long, and there is not much exertion beyond hanging on.


You exhale at what feels to be a comfortable rate on the way up....it is actually quite intuitive....it is as easy as exhaling :)

Ears clear fast going up...None of us EVER had any problems on Blow and Go ascents....this is a non-issue.

This depends on how long you put them in pressurized water...how long from when the submersible lets all the water in that shrinks the air space, and compresses the air to your equilibrium with the 400 foot depth. If you can limit this to maybe 2 or 3 minutes ( sort of required so that they can equalize their ears as the pressure comes up--they will need to squeeze their nose and blow non-stop into their ears)...Keep the whole bottom time under 5 minutes and you are still in the range of what freedivers have done without DCS.....take it to 10 minutes and DCS is most likely going to happen, and require O2 on the surface, then a chamber ride....or at least a bottle of O2 they can go back down to 20 feet with and hang out for 20 minutes.

No need for an OPV with an open bottom bag.....look up some of the open bottom "lift bags" online. Dry suits would need an OPV, but pulling the neck seal or wrist seal open will manually dump instead.View attachment 207962

Awesome!

And one last thing - is using PSI in language/measurement instead of ATM a real no-no, or does it depend on country/diver?

The high number value of PSI to its equivalent ATM makes a much more dramatic statement.

Thanks.
 
Awesome!

And one last thing - is using PSI in language/measurement instead of ATM a real no-no, or does it depend on country/diver?

The high number value of PSI to its equivalent ATM makes a much more dramatic statement.

Thanks.
I don't really think it matters to divers which they hear.....the psi they would be experiencing or the number of atmospheres....this is something that we don't consider that much.....of on scuba, you don't actually "feel" any pressure, except with ear and mask clearing ( which you never allow to become much pressure by continual "equalizing")...and as a freedivers, even then you don't have a reason to consider the numbers--you just keep blowing air into your ears on the way down ( and a bit into your mask)...and on the way to the surface from the bottom, everything takes care of itself, with no input from the freediver....Sort of like we don't need to know that our jaw muscles need to be able to achieve 2000 psi of pressure for us to be able to chew up a steak---we just "do it"... :)

For your film's audience, use whichever number sounds more dramatic. Either will be abstract to the audience.

---------- Post added May 6th, 2015 at 08:21 AM ----------

Another opportunity you have for the film, is that as the protagonists flood the submersible....and the air pressure begins to reach equivalence with the water 400 feet deep....your people will become MASSIVELY Narced! One could be so narced he could not remember how to walk...imagine a drunk trying to get up steam, to make it up 4 steps.....Everything they do, requires all their concentration, and if they get distracted from the main objective, they can easily forget what they are supposed to be doing. One could easily get entranced in watching a drip or a fish outside the porthole--as if it was the most beautiful thing in the world--true art, and everything else would cease to exist for them. They might entirely forget their life was in danger, and that there were only minutes left.

Some could be very brave--like drunks afraid of nothing.....another might have gotten a "dark narc", and could be terrified of everything around him...almost paralyzed with fear.
And, there are some people that are like "high functioning drunks" at 400 feet....able to do most simple tasks ok, and able to stay on "mission".....you need at least one of these for them to succeed.
 
Another opportunity you have for the film, is that as the protagonists flood the submersible....and the air pressure begins to reach equivalence with the water 400 feet deep....your people will become MASSIVELY Narced!

Although a cool idea, I'm afraid the point would be lost on a non-diving audience, at least without some kind of priming and/or explanation. AFAIK, not many non-divers are aware of nitrogen narcosis, much less the different ways it can manifest.



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Sharks. I'm not hearing anything about sharks. There's gotta be sharks for it to work.
 
When the protagonists first flood the submersible....when they first get exposed to 400 foot deep levels of narcosis.....This hits you SUDDENLY.
When I began my deep diving back in the early nineties, I had been doing 140 to 160 foot stuff for a decade or more...as if it was nothing.....then hooked up with some famous deep divers that brought me on a 260 foot wreck dive, and let me use some of their old gear--the doubles, etc....

I remember falling heavy, like a sky diver---we had to do this to reach the wreck in the big current----- we had to fall fast....(around 150 feet per minute or faster).

So suddenly the bottom loomed up, I inflated the bc almost all the way to stop the fall to the bottom....and landed on the deck of the ship at 260 feet deep....and was just standing there with my huge double barrel Ultimate Speargun in my hands, carried much like a Nato Assualt rifle .....Instantly, a huge wave of narcosis hit me....it was like I had been at a party, and had just done a line of cocaine 10 feet long.....My head was exploding but without pain....big waves of narcosis had me reeling.....My buddy George suddenly swims by....after I had been standing and experiencing these waves--it could have been 4 seconds or 4 minutes...but I am fairly certain it was 4 seconds because of the behaviors of the group....My buddy George swims overhead, and points to a huge black grouper over 70 pounds, and motions to me I should follow and shoot it with my speargun....I "get" this, and decide to swim after the huge fish...but am so narced, I don't remember how to swim....I lean forward, and half fall forward, then catch myself a few times in a row, before I remember how to swim.....however long this takes, I am suddenly swimming. I go into "hunting mode", and all thought of narcosis is replaced by "the Hunt"....I find I have the brain power to track/follow the fish, to check my air pressure, and to check my dive computer every few minutes for elapsed time--knowing at 25 minutes we have all agreed that we re-form as a group at a specific place on the wreck, and then we do "Blow and Go"....So these 3 things I can do...and it works like juggling, right up until I shoot a fish, and add a 4th element....and now the other tasks are lost--no longer being thought about or juggled.

And then I am being "wagon-trained" by about 15 big grouper, circling me as I attempt to put my just speared grouper on my slinger....my coordination is so bad, I keep fumbling, for what seems like forever, and am going as fast as I can, because I want to get the spear back on the gun, and shoot more of the groupers that are wagon training me...I manage to shoot a couple more....time stops....nothing else exists but the shooting and wagon training, and the slinging of the fish....and then what could have been an eternity later, I am rocked by a big hand pulling hard on my shoulder--it is George --he gets eye contact with me...makes a sign like--look at the computer, what are you thinking--it is 26 minutes--I am a minute late in forming up for the group to do Blow and Go....He gestures like he is hitting his head...like saying "you dummy" , but with a smile.....

The 6 of us are together on the deck at 250 or so, and at the signal, we all fully inflate our bc's.....In the next instants, we are traveling upwards so fast that it seems impossible....Air is escaping from my mask, but this is nothing compared to the ear splitting noise being made by my OPV on my BC.....the high pitched shriek is from something like a firehose of air coming out of the BC, and a monster is chasing us from below, fed by this onslaught of air blasting into it....it is like a wall moving up just below us, vortexes and swirling everywhere....and the huge noise of the shrieking.
I am still narced--it is a great narc though....you feel amazingly content....you are having your best, most euphoric day ever, and you are definitely living in the moment :)
My two tasks to perform, are continual exhales, and watching my dive computer to begin dumping all air from the BC at 100 feet--to reach a dead stop.....We all stop dead at 100 feet from the surface, the wall of bubbles blasts through us....blows us around like the wind of a hurricane...and then it is gone, and replaced by the calm after the storm.

We settle in to a short wait at 100 feet, then a slow swim to 50 feet where we will do out first ten minute stop.
Even at the 40 foot stop 12 minutes later, I am still blasted and euphoric from the narc...it has not yet dissipated yet, so extreme was the narcosis.
At the 30 foot stop, each of these around 10 minutes long, all the other divers are spinning around 360 degrees, afraid all the bloody fish I am carrying, will bring sharks in...so they are all eyes....I look around, but feel so good that I see this as great fun....but do have the huge double barrel gun ready, just in case.
By the time we are at our final 20 foot stop, and have switched to pure O2, all narc is well past...and has been replaced by boredom of waiting for the deco stops to be over.

When we climb onto the boat, there is still the great feeling from the high O2 and the narc though....we feel like kids out the night of their Junior Prom....there is no pain, no discomfort, only adrenaline, satisfaction, and excitement.....and "the WHEN" of when we are going to do this AGAIN ! :)

Just thought I'd share some of the experiential part of this depth with you :)
 
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Sharks. I'm not hearing anything about sharks. There's gotta be sharks for it to work.
Squid. Giant squid.

Oh, and Bisset. Jacqueline Bisset.
 
Squid. Giant squid.

Oh, and Bisset. Jacqueline Bisset.

She is a little long in the tooth for this one. Scarlett Johanson.
 
Just to reinforce what danvolker said about DCS . . . one of the keys to avoiding it appears to be minimizing the time from the start of compression to the surface. The test ascent from the Orpheus in 1965 was from 475 feet. Compression (that is, flooding the chamber and compressing to ambient pressure) took about 25 seconds. Then an additional 4 seconds of "bottom time" while the hatch opened and the person started the ascent. Ascent was at 3 ft / second, so a total of about 160 seconds for the actual ride to the surface. Total time (25+4+160) = 189 seconds, or just over 3 minutes start to finish. No reported narcosis or DCS. BTW, some of the later trials involved ascents at up to 8 ft / second.

Apparently, with rapid compression followed directly by an ascent, the body doesn't get the full depth hit until after you're on your way up. "In such a rapid escape, the circulation time becomes an important factor. If we assume that the blood takes 10 seconds to travel from the lungs to the tissues, there will be a similar lag between the ambient pressure and the arterio-capillary blood gas tensions. Thus when the ascent commences [after 25 seconds of compression] the arterio-capillary blood gas tensions would be only 160 ft. sea water and when the arterio-capillary blood gas tension reaches 500 ft, the subject would already have ascended 60 feet from the submarine. When the subject surfaces the arterio-capillary blood gas tension would still be 83 ft. of seawater"

And, FWIW, here's a chart from the 1970 report on various trials that seems to show that the odds of a DCS hit are relatively small if the end-to-end time is short (eyeballing the chart, it looks like 2 DCS incidents out of roughly 50 trials with some of the trials involving multiple subjects). One bit of terminology on the chart "decompression time" means time spent in the actual ascent from depth.
DCS Plot.jpg
 
All very interesting.

I think I could probably use the narcosis actually, if they were expecting it and had planned a fail-safe. With a rapid ascent, how long would they still feel it once they surface? I need them (or even just one) at least partially lucid to flag down rescue.

Is the effect of narcosis the same with everybody, or does it vary depending on the person? It sounds like it can be controlled somewhat with anticipation and mental focus? Could even flip it so the more experienced crew member anticipates it but gets it worse than the rookie...

I'm avoiding sharks, but it sure would be funny if they shot up straight through a group of them and spooked them to heck.
 
All very interesting.

I think I could probably use the narcosis actually, if they were expecting it and had planned a fail-safe. With a rapid ascent, how long would they still feel it once they surface? I need them (or even just one) at least partially lucid to flag down rescue.

Is the effect of narcosis the same with everybody, or does it vary depending on the person? It sounds like it can be controlled somewhat with anticipation and mental focus? Could even flip it so the more experienced crew member anticipates it but gets it worse than the rookie...

I'm avoiding sharks, but it sure would be funny if they shot up straight through a group of them and spooked them to heck.

While they do spook, they immediately come back around to see what spooked them. They are apex predators after all. Some don't see very well, so they check out new things by tasting. Hard on the stars.

I'm giving you crap about the sharks. A nice Kraken, though.....
 

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