This is a new and one of the cutest io games. Oceanar io is an underwater agario like game, but with much nicer graphics and new features. In oceanar io you play a cute fish, you eat fish food, get bigger and make baby fish. The baby fish are your army and you need to use them to attack other fish.
Use your space bar and the left/right mouse buttons to control your baby fish army. Right mouse button to merge smaller fish into bigger ones and the left button is to attack.