Armed Sea Hunter

WATER
After damage calculation, if this card battles an Effect Monster: Negate the effects of that monster (including in the Graveyard). You must control another face-up WATER monster to activate and to resolve this effect. If this card would be destroyed, you can destroy 1 face-up Level 3 or lower WATER monster you control instead.
1800
400

Sea Serpent WATER Effect Monster 4 effect