This stuff is a nylon-like plastic that is completely malleable at low temperatures. When it hardens, it's a very tough, durable plastic, but you can turn it back into a play-doh consistency by pouring boiling water on it. It struck me as useful for making model buoyancy chambers and other parts for tub to pool-size models.
What does it do at temps of
What does it do at temps of (say) 40C? There are areas where the seawater will be that warm (and warmer).
I wouldn't actually use it
I wouldn't actually use it in the ocean, I'd only make very small models out of it, e.g. to test buoyancy designs in a pool.