Slice fish is the third stage in Ninja Fishing. The player must slice every fish in the area and keep an eye on the dynamites. Every fish can be cut with a specific number of cuts, and the number of cuts needed to cut each fish gets reduced for every upgrade of the katana.

If a player had caught a treasure chest, a treasure chest may come at some point in some point of this stage. If a treasure chest is fully sliced, either a large sum of coins is received, a treasure is released, or a radioactive can is released. If a treasure is released, the only way to claim a treasure is to slice it, in which the player can own that treasure. A radioactive can must not be sliced or else no more fish can be sliced from the catch.

If a dynamite or radioactive can is sliced then no more fish can be sliced from the catch, but will still receive all other coins and prizes prior to the explosion.