lamont:
what about having ditchable weight to be able to respond to a flooded drysuit? (and either a ripped BCD, or a double malfunction that takes out the BCD)
Lamont,
If you flood your drysuit you'll be cold. If you're cold enough long enough you'll go hypothermic, but that's a different issue.
A flooded drysuit,
if its being used properly (e.g. just enough gas inside it to offset extreme suit-squeeze), would actually alter the diver's bouyancy very little. The drysuit provides thermal protection, mostly, not bouyancy. The diver uses the BC or wing for bouyancy. Flooding your drysuit would present thermal problems, true, but not necessarily significant bouyancy problems.
A failure that compromises the BC/wing is different - for example, a corregated rubber hose pulling out of the fitting where it connects to the BC, or a slit caused by encountering a sharp edge in a wreck.
Leaving aside the probability of such things occurring, IF they occurred initially there are the same considerations outlined above. The diver cannot surface regardless. The diver must first exit the cave or wreck and/or complete the required decompression before surfacing anyway.
A loss of bouyancy can be problematic, but not in all cases. Caves have floors and wrecks have decks - the diver is not going to sink far. In either case they could hand over hand out. A deep dive off a wall may pose more immediate concern.
This is one reason why technical divers carry liftbags and/or Surface Marker Bouys (SMB). There are numerous options to respond to loss of bouyancy: 'deploy the bag on a reel and swim up while reeling in'; 'attach the device to a crotchstrap D-ring and achieve neutral bouyancy with it' (try it before saying it can't be done - if you work at it in a quarry it
can indeed be done with practice); and so on...
More importantly, technical diving is done in teams. Not merely buddy pairs, the idea of team implies a group of divers (two is only a minimum, three is almost always better) who regularly practice together, 'chalk-talk' or discuss dive planning and emergency response together, and conduct dives together as a team. Should the things you suggest occur to one member, it is the team that responds collectively to bring everyone home. The team is the ace in the hole for almost any problem any individual member could have.
Hope this helps,
Doc
