Idk if it's close enough but it is native and nature focused, !nolawns@slrpnk.net I know Mander had some but, RIP to that. I think Beehaw has a few nature related communities and I know Lemmy.world has a bunch of animals covered like !bats@lemmy.world and !foxes@lemmy.world but that's not quite aquatic or amphibious. But maybe a good place to start searching?
I don't think this was direct help but, maybe inspirational help? Lol