Eelectric

Eelectric is a NES game inspired by the classic Snake. Move the electric eel across the water, waiting for piranhas to show up. When they start biting - which reduces your HP - press "A" to shock them. Then the eel can eat those piranhas - and only those.

Unlike the original Snake game, here you don't lose when colliding with the walls (nor with yourself), instead you just stop. But staying stopped means the piranhas will have a field day :)