Gobbler

Gobbler is the boss found in Olive Ocean.

Stone/Smash

Hold right after dropping into the arena and bounce off of the platform. Attack once you're above Gobbler. If Gobbler moves, jump out of the water and attack again. Otherwise, squirt at the boss until it is defeated.

Bouncing off of the platform allows you to time an attack on Gobbler and defeat it before Gobbler can react. This is only if you land perfectly on its fin and only if Gobbler spawns fish.

Sword

Sword is the recommended backup ability to use in case Stone or Smash is lost. It can be grabbed either with a Sword Knight in the previous room, or with the trophy right before the boss.

Defeat Gobbler by performing uppercuts on the ground in the water. If Gobbler approaches the ground, perform neutral swings instead. Compared to Stone or Smash, Sword loses a few seconds depending on Gobbler's behavior.