I tamed one of these named Diana. She was super fast but kind of stupid: always getting stuck on something. Diana and I formed somewhat of a relationship as time went on. Our bond strengthened she was able to beach a shark for me to kill it. Diana soon became one of my best friends... but nothing lasts forever. As I was leading her back to base via SS Dodo, I noticed a large figure swimming rapidly towards us. Diana made the fatal mistake of not paying attention to her surroundings. I helplessly fire arrow after arrow at it, but it was so filled with rage that they had no affect. I had to watch as MY Diana was ripped to shreds by an oversized fish. That is why my base is now called Fort Diana in honor of the brave soul. Thank you for your time.
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!