Beefy, powerful, fast, good lifter, supports platforms, can be tamed on foot with much less efort and risk than Mosas (still not easy). For sure this thing is the most versatile mount after Mosas, Quetzals, Wyverns and Mantis (oh boi, you NEED a Mantis).
ATTENTION! IF YOU COMPLETE NO AIR PURSUIT, YOULL GET A MADTERCRAFT PLESSI SADDLE, AND 10 LARZUS CHOWDER ON MOBILE! MOBILE NO AIR PURSUIT ONLY GIVES MASTERCRAFT PLESSI SADDLE.
I manged to get into a river because these dudes can levitate and don't take damage so the poor bobs saw the unspeakable as the loch Ness monster ate them with this long butiful neck of terror.
Someone who said "you can only get mastercraft plesi saddle and 10 lazarus chowder when completing no air pursuit" that's a lie. I get ascendant plesio saddle
To the guy that had his plesiosaur twisted into a ball, just return to the menu and load your save file again to fix it. I had it happen after I finished a mission on Genesis.