If "Umi" is on the field: You can activate this effect; your WATER monsters can attack directly this turn. During your opponent's Battle Phase (Quick Effect): You can target 1 face-up monster your opponent controls; destroy it. If this card on the field is destroyed by battle or card effect: You can either add to your hand or Special Summon 1 WATER Warrior monster from your Deck or GY. You can only use each effect of "Mega Fortress Whale" once per turn.