Hungry Shark Arena is an eat-and-grow game with teeth: you're a shark in a busy arena, and you eat everything smaller than you while avoiding whatever is bigger. Growth changes what's food and what's a threat.
It's the food-chain mechanic in an arena rather than an open ocean, which keeps the encounters frequent — there's nowhere to hide for long.
Eat continuously. Small fish grow you steadily and smaller sharks grow you quickly, but contesting anything near your own size before you're clearly bigger is how runs end.
You share the arena with other sharks in real time, competing for the leaderboard.
Yes — it runs in the browser with nothing to install.