Keep moving around the arena, clear smaller piranhas before they surround you and return damage to the boss only when the route is open. A shotgun is useful for close groups; TNT is optional, not required. After the kill, carry the distinctive skull- or tail-like trophy to the quest giver instead of ordinary meat.
Prepare before the lure
- Bring healing food and ammunition.
- Use a ranged weapon you already control; an upgraded shotgun is a practical crowd-clear option.
- Clear unrelated creatures from the arena.
- Pick a wide loop with no shoreline dead end.
- In co-op, assign one player to watch smaller piranhas and one to collect the trophy.
Fight plan
- Begin moving as soon as the encounter starts; do not wait for the group to surround you.
- Keep the boss and smaller piranhas in front or to one side of your route.
- When the smaller enemies close in, use the shotgun or controlled shots to reduce their number.
- Return damage to the boss while the lane is clear.
- Move again before reloading or before the next group reaches you.
- Repeat the same loop instead of improvising through clutter.
TNT can shorten a crowded phase if placed safely, but throwing explosives while trapped often creates another missed damage window. Treat it as a planned tool, not the core strategy.
Co-op roles
- Runner: keeps the boss moving along the outside route.
- Crowd control: removes smaller piranhas that cut off the runner.
- Damage: attacks from a different angle when the boss commits to the runner.
- Collector: picks up the distinctive trophy immediately after the fight.
After the fight
Pick up the unusual skull- or tail-shaped boss part first. Return it to the relevant second-island quest giver before selling meat. If the hand-in fails, check every distinctive part in all co-op inventories before summoning the boss again.
Continue with Island Progression and prepare your next loadout with Weapons and Upgrades.
Sources
- How to Fish on Steam — Dazed Games / Valve — https://store.steampowered.com/app/4001890/How_to_Fish/ — bosses, combat and island progression.
- How to Fish General Discussions — Steam Community / Valve — https://steamcommunity.com/app/4001890/discussions/ — smaller-piranha, shotgun, TNT and trophy reports.