The 3 tins of fish locations for Fast-Flowing Waterworks in Kirby and the Forgotten Land are in the screenshots as follows:
Tin of Fish 1 – Stand on the sparkle to reveal location
Tin of Fish 1
Tin of Fish 2 – Use Stairs ability next to this hole, the tin of fish is inside when you break the fire crates. There’s ice enemies that let you shoot ice to break these.
Tin of Fish 2
Tin of Fish 3 – Stand on this switch and the tin of fish will be swirling around the whirlpool here.