You can’t have a Legend of Zelda game without an underwater dungeon of some sort, so naturally the boss fight of the water dungeon in The Legend of Zelda: Link’s Awakening would have to be underwater, especially after you obtain the Flipper item that allows you to swim part the way through the dungeon. The boss fight against Angler Fish is exactly that and this guide will detail how you can take down this angry fish.
Swimming can take some getting used to due to the slowdown compared to normal movement, so that’s going to be your first hurdle to overcome here. If you don’t know the controls, you can move generally by using the right analog stick, while press A will make you swim faster in a direction. Pressing B will then slash your sword, which is how you’re going to attack Angler Fish here.
To start the fight, just go down and keep attacking the light on its head with your sword over and over, constantly chasing after him when he swims away. In addition, watch out for falling debris that comes down along the way too.
Eventually, Angler Fish will summon additional smaller fish, but these can just go down quickly with a slash of the sword as well. So just take them down and then move back to worrying about the boss. Keep hitting him with your sword and eventually he will go down and reward you with the Heart Container and the Surf Harp for your troubles.