Cat Shark

2 Level 2 monsters
While this card has an Xyz Material attached that was originally WATER, it cannot be destroyed by battle. Once per turn, during either player's turn: You can detach 1 Xyz Material from this card, then target 1 Rank 4 or lower Xyz Monster you control; its ATK and DEF each become double its original ATK and DEF until the end of this turn.