If you’re planning on taming one of these, don’t do it behind the snow biome unless you have a lot of bio toxin (preferably a stack or two just in case, depends on the lvl.) and make sure to have a swift mount that can dodge the attacks of the said Moss, such as a plesiosaur or something faster. If you do happen to knock one out in the snow biome ocean I suggest you go up for air and wait for 30 secs, (and for health) then go down and wait for 30 more seconds and feed it bio toxin. Keep doing this until it is tamed, Usually his strategy works.
Happy taming! :) Hoped this helped.
Center tip: as they have added the mosa to the center I've found the easiest way to knock one out is find one close to the bubbles get its Agro and swim in the bubble the mosa will get stuck and it can't hit you. Also this gives you unlimited oxygen and sanctuary from being attacked by anything else. ðŸ¤˜ðŸ¼