Guppy by Christiaan Moleman

Guppy is a 2D watercolour fish simulation.
Swim like a fish! Move your tail left and right to propel yourself through the water, hide in the shade of lilies and venture carefully into the open in search of food. Try not to get eaten.

CONTROLS:
Alternate LEFT and RIGHT ARROW (player 1) or A and D (player 2)
NOTE: Also supports GAMEPAD and TOUCH  (mobile)
Co-op only supported on desktop (Win/Mac/Linux), not mobile.
TIP: If you prefer swimming around in peace you can also remove predators in the options (ESC > Main Menu > Options), though this disables scoring.