I don't know much about them myself, so I'm not sure. If they can't survive in both, it could be he found it at the mouth of a river on the coast and didn't realize the need for saltwater himself, but I really don't remember the fine details. He was an elementary school teacher I had nearly 20 years ago, so the memory isn't fresh by any means.

It's anecdotal but I had a gradeschool teacher who claimed to have found a frozen one that he brought home to keep its exoskeleton. He left it outside to thaw while he did some errands and came home to find his dog losing his shit because the thing was alive and running around in his backyard. I think he said he took it back to the river afterward.

Dude was a pretty sincere guy who doesn't strike me as the type to make something like that up, so I personally take it as true. I'd say there's a non-0% chance the one in OP's pic is alive.