For each match, one person is randomly assigned to play the shark and everyone else is a human trying to work together to stay alive. According to the Infested Waters page on Roblox's website ...

New redeem codes have dropped for the "Roblox Shark Game," and they give prizes up to 10K cash. All of the redeem codes in this round give away cash to players. 'Roblox Shark Game' Takes Iconic ...

The shark can also, apparently "tail whip players ... A Roblox farming game made by a teenager 'in like three days' had 8.9 million players online at the same time—Steam peaked at 11.5 ...