Harpoon a Fish Fish Index: What Fills an Entry and How to Catch New Fish

In Harpoon a Fish, an index entry fills the moment you catch that species with your harpoon. The index tracks over 1,800 unique fish, and the first time you land a species you haven't recorded before, its entry is filled — the catch itself is the whole act. Everything after that, like growing the fish in your aquarium, is a separate activity and isn't needed to record the entry.

How to catch a fish for the index

The documented harpoon catch takes two moves:

1. Aim at your target and fire.
2. Time your reels to pull the fish in.

That's the catch loop for everything swimming in the water, from ordinary fish up to sea monsters, and every completed catch counts toward your species records. If you're still learning the timing or the controls, our Harpoon a Fish how-to-catch-fish guide and how-to-play overview break the basics down further.

Where new species come from: sink deeper

The game's discovery loop pairs two ideas: get fat and sink deeper to discover and catch new sea monsters. In practice, a fatter fish can sink lower, and deeper water is where species you haven't caught yet appear — including rarer sea monsters.

Two things to keep in mind while you descend:

• Deeper means rarer finds, but also more danger. The deeper you go, the more risk you take on alongside the better catch pool.
• There's no published depth requirement per entry. Deeper water is simply where new species show up, so the practical approach is to keep pushing your depth down and catching whatever you don't have recorded yet.

The aquarium is optional for your index

Once a fish is caught, you can put it in your aquarium and grow it as a pet — that's the game's raising and evolution side. But no aquarium step is required to fill an index entry: the record is completed by the catch. Treat the two systems separately — catch unknown species to fill the index, then choose your favorites to grow. If you want the follow-up, see how to grow fish and our fish evolution coverage.

While working through missing entries, it's also worth checking our codes page for the latest active codes before a long session.