Best for killing scorpions on bottom of ocean floor since they don't take torpor. Scorpions down there will knock any other animals out. Once you kill it, hit it with a pickaxe to gather black pearls. Very useful for the next update with tek gear.
Since there's no way to post it on the actual creatures wall I think I should warn everyone whilst taming these beautiful ichthyosaurus watch out and I mean watch out for any Cnidaria jellyfish they will shock you to oblivion I was caught taming when 4 of these guys jumped me and I absolutely freaked out
So yeah Cnidaria are easy to kill but keep your distance!
Easy enough to tame that you don't need to trap it.
They're attracted to players and especially tames, so using anything from a turtle to a mosa makes taming them easy. They may swim off, but are easy to magnet back onto your tame.