Ep 37: Return to the Depths

That was a ton of fun. I love doing voice-over work and almost never get the chance. Thanks, DM Mitch, for the invitation! 

Hey Rich, got a technical question.

In the real-world, besides sunlight exposure and vision issues, what physiological downsides would there be for an deep-water aquatic creature coming to the surface? I have to imagine the immense pressure differences would cause some issue, no? I remember what you said about Sperm Whales deflating their lungs when they dive, but I can't recall hearing the reverse issue being touched on in the pod.

<releases the Kraken on umbralwalker>

<cancel that, releases the sharcroctopus!>

Great question.

The exploding fish is actually true. That has to do with something called a swim bladder that most fish have. It's a bladder in their bodies that acts like a BCD (buoyancy control device) for SCUBA divers. The fish can add and remove air from the bladder slowly by this strange diffusion process from their bloodstream. That's why fish don't sink like a rock, or have to fight to stay where they want all the time. The problem is that the diffusion process is slow so when you bring a deep sea fish up to the surface, it is exactly like filling a balloon (or a diver's lungs) up with air at depth and bringing it up. The reduced pressure causes the air in the balloon (or lungs) to expand and if it can't get out, the balloon explodes. 

en.wikipedia.org/?title=Swim_bladder

If a deep sea creature like a colossal squid is allowed time to adapt to the various pressure changes, it will likely survive fine. If it's caught in a deep sea net and forced to the surface quickly, I imagine it would have numerous issues.

If for some reason, for example, a SCUBA diver is running out of air and has to get to the surface quickly, they are trained to take as deep a breath as possible from their all-but-empty tank or pony bottle (backup tank), throw their head back and shoot to the surface. The pressure change is likely to cause you to blackout, but as long as your trachea is open, the air in your lungs that's expanding 1) can get out, and 2) will prevent water from getting in. That is an "I'm going to die otherwise" maneuver, though. If you do that with your head pitched forward, pinching off the escape route, your lungs will explode.

Not all creatures have swim bladders though, so if you're dealing with a fantasy D&D monster you just have to decide a little bit about their internal physiology. Creatures that don't have swim bladders might have other pressure-related issues, but as I mentioned in, I think, ep 37, I don't know how much research has been done on it.

As far as scuba diving goes (and this might not work for the giant squid, kraken, or sharcrocdopus) it takes a couple of minutes to adapt for every couple (5-10 I think...) meters (I believe pressure change is noticeable around 15 meters, but don't quote me).

It would be cool to put a character through a "recompression spell". A group of wizards have to use this spell to cure sea travelers of decompression sickness. An idea.