When this card is Normal Summoned, put 3 counters on it. This card cannot be destroyed by battle. If this card attacks or is attacked, remove 1 counter from this card at the end of the Damage Step. If you cannot, destroy it. Once per turn, during your Main Phase, you can change 1 face-up Attack Position monster your opponent controls to face-up Defense Position.
These cards can be used to Summon B.E.S. Crystal Core without a tribute. A Legendary Ocean reduces the level of all WATER monsters in both players' hands and on the field by 1 which makes B.E.S. Crystal Core level 4. Pay 1,000 Life Points instead of tributing a monster by using Mausoleum of the Emperor.
It, Fisherman 2 and Plesion are really the only particularly good Level 5 WATERs in Duel Links right now. I guess Giga Gagagigo would be a distant third. Maybe Shark Cruiser is worth considering, though I personally wouldn't. You could go Bottom Dweller for the meme value I suppose.
new pack with some water support + this gonna be boom