Full progression spoilers

This walkthrough names every island boss and the final transformation sequence.

1
Island 1

Shipwreck Shore

Bring a beer to the shipwrecked captain, use the returned Empty Beer Can to catch the Spider Crab, then collect the keys that advance the route.

Route objectiveRecover the boat keys
2
Island 2

Forest Island

Find three leeches in the tall grass, hand them to the woman, use the Leech Bait for Giant Piranha, and return the boss tail to finish her request.

Route objectiveComplete the forest dinner quest
3
Island 3

Vacation Island

Catch an endangered species such as Needlefish, Seahorse, or Bowlfish. The tourist gives you the Carrot needed for the Pufferfish encounter.

Route objectiveHelp the tourist
4
Island 4

Military Island

Use the Professional Boss Lure to catch a Tuna, then place the Tuna in the center of the military island to trigger the boss.

Route objectiveDraw out the Albatross
5
Island 5

Volcanic Island

Give the scientist five different fish for a Fish Bucket, catch the Bowhead Whale, carry it up the volcano, and drop it into the lava to begin the final encounter.

Route objectiveTransform the whale
Before you sail

Five island exit checkpoints

The boss kill is only part of each unlock. Most islands require a dropped item to be returned to an NPC before the next radar coordinate appears. Use these checkpoints before leaving the shore.

I1Buy or upgradeCrab-Fishing Rod, Beer, radarReturn before leavingSpider Crab ShellI2Buy or upgradePistol or Shotgun, engine upgradeReturn before leavingGiant Piranha quest dropI3Buy or upgradeUzi, Standard Lure, inventory slotsReturn before leavingPufferfish FinI4Buy or upgradeProfessional Lure and Boss LureReturn before leavingAlbatross HeadI5Buy or upgradeScientific Lure, Assault Rifle upgradesReturn before leavingFinal boss tail

Buy the radar on Island 1

Boat Keys let you move, but the radar shows the new destination. In co-op, a passenger can navigate while the host drives.

Keep one weapon upgrade path

Spreading money across every gun slows progression. The Shotgun helps early, the Uzi carries the middle route, and the Assault Rifle is the final-boss investment.

Return every boss item

Spider Crab Shell, later boss drops, Albatross Head, and the final tail are quest triggers. Picking them up is not enough; complete the matching NPC hand-in.