If this card is used for the Xyz Summon of a Number monster, it can be treated as a Level 3 or 4 monster. If this card is in your hand or GY: You can target 1 WATER monster on the field; Special Summon this card (but banish this card when it leaves the field), and if you do, halve that monster s ATK, also, you cannot Special Summon monsters from the Extra Deck for the rest of this turn, except Xyz Monsters. You can only use this effect of Crystal Shark once per turn.