Time between 130-foot dives?

Hi everyone --

I'm a novice recreational diver who hasn't gone out in a decade. I'm also a novelist, and my protagonist works in salvage. She's trying to being a large (6x6x6) safe out of a recently sunken megayacht without anyone knowing what she's doing, so she has to do it all clandestinely. The boat's in about 130 feet of water, and I'm wondering how long she would need to wait between her dives. Could she do them on consecutive days? I figure she's got about 10 minutes of bottom time each dive without decompressing stops, so it'll take a several dives to attach the flotation devices.

Also, if anyone knows, I'm thinking of her killing the bad guys in the end by attaching one of those flotation devices to them at 130 or so feet and inflating them -- sending them up fast. My thinking i that if someone went up that fast without a stop, they'd either get the bends bad (in open water, with a cut on their leg, so sharks) or an embolism. But that's not crucial yet -- I can find another way to kill them -- but I thought that might be cool.

Any information or advice anyone can offer I'd sure appreciate. Thanks

whiporee:

Any information or advice anyone can offer I'd sure appreciate. Thanks

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The bends rarely kills people. Instead, you might have a runaway ascent that sends them up, they get paralyzed from the bends, and somehow, because of the lift bag, they get stuck just below the surface upside down....paralyzed...with plenty of air. This is if you really want to punish these bad people. Just sayin'....

(Actually it usually takes some time before the bends "kick in", so I don't know that this scenario would follow reality)

You have just enough information to kill the both of you. Keep it to 3hours SI between dives and someone might actually survive.

Or get qualified divers to do it ;-)

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Bopper:

The bends rarely kills people. Instead, you might have a runaway ascent that sends them up, they get paralyzed from the bends, and somehow, because of the lift bag, they get stuck just below the surface upside down....paralyzed...with plenty of air. This is if you really want to punish these bad people. Just sayin'....

(Actually it usually takes some time before the bends "kick in", so I don't know that this scenario would follow reality)

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It is much more likely that the divers would be injured by a chest/lung expansion injury. Air expanding in the chest cavity will most likely cause Pnuemothorax, Mediastinal emphysema or Arterial Gas Embolism (AGE). All can be fatal. Pick one - your choice as an author.

The bends sounds the most dramatic but may be the least of their problem.

If the boat is in 130, the safe could be at 110 or so. They could dive 30% Nitrox at 120 and still have a PO2 of 1.4. The SI on some boats would be about 2 hours or so. give or take a bit.

Do the bad guys have a support boat at the surface? Note that if hero could pop their weights as bad guy started up you would speed up the ascent.

Could shoot an SMB that comes up so that the bad guy is between boat and SMB. Give the bad guy some sort of bang stick. Bad boat rushes toward SMB, hits and finishes off bad guy in water, bang stick goes off and puts hole in the boat and the props hitting the tanks on the diver trash the engine.

Steve_C:

If the boat is in 130, the safe could be at 110 or so. They could dive 30% Nitrox at 120 and still have a PO2 of 1.4. The SI on some boats would be about 2 hours or so. give or take a bit.

Do the bad guys have a support boat at the surface? Note that if hero could pop their weights as bad guy started up you would speed up the ascent.

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No support ont eh surface where they end up. The boat is early, when she's getting the safe. She hides it in a Bahamian cavern, and the bad guys are going with her to retrieve it. They aren't experienced -- none of them are -- but they don't trust her enough to let her go on her own. So as she's taking it out of the cavern, she cuts it loose -- lets the safe fall the mile to the bottom of the sound, and through some plot device has the bag attached to the bad guys (it'll just be two of them).

I had thought embolism, but didn't know whether getting shot up by the bag would be fast enough to cause one if they were remembering to exhale.

So just to follow up, when she's getting the safe out, she could dive to that level on consecutive days. Any other tidbits of being down 130 or so feet anyone can share -- color tones (it's in the Bahamas), would doors be able to be opened, stuff like that. Just want to get the facts as close to correct as possible.

Thanks again -- Matt

At that depth she will be narced so her thought processes will be slowed down. She will have to avoid working too hard or she could overbreathe and get CO2 issues. The narcing would require her to focus more. Harder to keep track of time. Harder to stay on task. Especially if she is not used to it.

---------- Post added January 19th, 2014 at 08:28 PM ----------

There is a lack of color at the depth. Stuff will look blue/green. The eyes and mind can trick you though. If a fish is supposed to be yellow and you see a bit of yellow you will think the fish is yellowish. Not saying you see it like normal but I was surprised when I got my first camera why there was less color in the pictures than I remembered seeing.

steve_c has a good point. The boat's in 130' but the safe won't be that deep unless it crashed through the decks and into the bilge. 110' does seem more reasonable.

6x6x6 safe is going to require quite the lift bag to get it out.

Are they breathing air? Or nitrox? Because you might want to follow up on the rest of steve_c's post about how if she is using nitrox she could extend her bottom time at 110'.

Water is deepish blue at that depth, don't forget that red, orange, yellow and green have faded to greyish tones unless you have a dive light.

---------- Post added January 19th, 2014 at 09:41 PM ----------

Yes you can open doors unless the boat's been down awhile and hinges have rusted, or parts of the wreck have collapsed.