Oceanar.io

Oceanar.io is a massively multiplayer game where players compete for dominance within an under-water ecosystem. Players eat various micro-organisms and shells to score points. As you eat, you begin to accumulate fish and can collect crabs and other ocean creatures. Then you can use your school of creatures to eat other players. But watch out, if another player eats your Queen fish, you die. You won’t be able to stop playing this amazingly addictive game.