How to Fish Mutated Bowhead Whale Boss Guide

The Mutated Bowhead Whale lives on Island 5, the Volcano, which sits directly north of Island 4 (the Rocks island), and your boat radar makes the trip easier. When you arrive, look for the NPC in the yellow hazmat suit. He asks you to catch five fish that are native to the Volcano, so buy the Scientific Lure from him, catch five local fish with your fishing rod, and feed them to him one at a time. After the fifth fish, he hands you the Fish Bucket.

The Fish Bucket is the bait that summons the regular Bowhead Whale. Attach it to your hook, cast your line into the ocean off the island, and the whale will take the bait; reel it in and the boss fight begins. The mutated form does not appear until that first whale is dead and its body is offered to the volcano, so the two fights are really one long encounter chain. The table below sums up the differences.

Buy the Assault Rifle before you summon the whale, and get at least a couple of upgrades for it, because upgraded ammo noticeably shortens the fight. The moment the whale surfaces, start moving: its opening move is a huge leap, and if it crashes down on you it eats away over half of your HP. Stay mobile and never stand where you were a second ago.

Once the whale lands, you get a short window to unload your bullets into it. After a few seconds it hops back into the air, and while it is airborne you have roughly two seconds to keep shooting before you must relocate again. This hop-and-crash cycle is its main attack, and the whole fight is about punishing the landing windows without getting sat on. Keep an eye on the white bar under the boss health pool, since if that bar empties the boss escapes and you have to start the fight over from scratch.

When the whale dies, pick up the carcass and place it in your inventory. Do not sell or discard it: the carcass is the key item that starts the final boss fight.

With the carcass in your inventory, use the wooden planks on the Volcano to climb to the top of the crater. Equip the whale carcass and throw it into the volcano. This immediately begins the final boss fight against the Mutated Bowhead Whale, a bigger and tougher version of the whale you just killed.

Before you throw the carcass, finish your preparation, because there is no warm-up once the fight starts:

• Buy the Assault Rifle if you skipped it, and add at least a couple of upgrades.
• Visit the military base and stock as many healing items as you can carry.
• Review the dodge pattern from the first whale fight, since the mutated form attacks the same way but hits far harder.

The Mutated Bowhead Whale is not only bigger and tougher than the first whale, it also hits hard enough that a couple of clean hits will kill you. Its signature new trick is spitting lava from its body, and getting burnt on top of the crash damage is what ends most attempts. Treat every leap as lethal rather than merely painful, and play far more defensively than you did in the first fight.

The core loop stays the same: keep moving so the whale cannot crash onto you, then punish it with your upgraded Assault Rifle whenever it lands or hangs in the air. Heal as soon as you take a serious hit instead of gambling on dodging the next one, which is exactly why the military base healing items matter so much. If you are playing in an online co-op lobby, which supports up to eight players, you do not have to face the final boss alone.

Expect a few failed attempts while you learn the lava timing. The same escape rule as other bosses applies here too: if you play so passively that the white bar under its health pool empties, the boss gets away and the fight resets.

When the Mutated Bowhead Whale dies, take its fin and feed it to the NPC in the hazmat suit. He rewards you with the key to the military boat. Board that boat and it takes you to the mainland, which rolls the endgame credits and completes the main story of How to Fish.

Finishing the story is not the end of the save. You can keep playing on the same file, and you retain every purchase and weapon upgrade you made, which makes it much easier to finish your fish collection and try for new skins from the roulette. If you enjoy speedrunning, there is also an achievement for defeating the final boss in under one hour; see the Bean achievement page and our full walkthrough for the route. For the earlier encounters, the bosses hub covers every fight up to this one.

• Standing still after the summon. The opening crash from the regular whale removes over half your HP, and the mutated form can kill you in a couple of hits.
• Skipping the Assault Rifle upgrades. The rifle with a couple of upgrades is the recommended way to burn the whale down during its short landing windows.
• Throwing the carcass into the volcano before visiting the military base. Walking into the final fight without a stack of healing items is the most common way attempts end.
• Ignoring the lava spit. Getting burnt on top of crash damage kills fast, so reposition instead of tanking the hits.
• Playing too passively. If the white bar under the boss health bar empties, the boss escapes and you redo the fight from scratch.
• Selling or losing the first whale's carcass. Keep it in your inventory, because it is the trigger for the final boss fight.