they look like their ancestors thought the end of the permian to be a bit of a laugh.
if the rope is 16mm poly as it appears to be and that gator is about 40kg the sea slaters are about 300mm long
after i thought wow my next thought was they have a fair bit of meat on em, i wonder what they taste like?
their small shoreline cousins are delicious, better than prawns or crab.
catch em like crayfish would need quite a rope or an ROV creel, bait it, sink it, wait until it pops up and phones home to be emptied and re baited.
typical human, find an interesting and venerable species and think traps n recipes
there are things in the fossil record very like them from before several major extinction events, chances are life will survive humans pretty well.