Sharks are marine animals that can be found in Grand Theft Auto: Vice City and Grand Theft Auto: San Andreas, though in these games they are completely non-interactive. This changed drastically in Grand Theft Auto V, where they can interact with and even kill the player.
GTA Vice City
Sharks appear in the ocean waters of Vice City. Like all marine animals in the game, these sharks are simply non-solid objects floating in the water and do not interact with any characters, vehicles, or other animals. Sharks spawn randomly in ocean water around the city; there are no preferred locations of spawning. They are completely non-interactive, and hence do not kill or even pose a threat to the player, and cannot be killed. The official manual of Vice City specifically describes shark attacks but shark attacks do not occur in the game at all. Like all other marina animals they are programmed to just drift straight forward through the water.
Shark attacks off Vice City happen a few times a year and there are more sharks out there than you would like to think - best advice: stay out of the water!
GTA San Andreas
Sharks reappeared in GTA San Andreas, their game mechanics seemingly unaltered from the previous game. They spawn randomly in the waters around the city and are again non-solid objects that cannot interact with the player. They can not harm the player and can not be shot at or killed by any other means.
Sharks appear in GTA V as hostile animals, capable of attacking and killing the player. They spawn at random in all depths of the oceans around San Andreas, particularly in Blaine County, usually by themselves or in groups of two or three. When a shark is in the area, it appears as a red dot on the map, and will circle the player or their boat in curiosity. If the player is swimming, the shark will continue circling, gradually getting closer. Eventually the shark will attack, but only if the player is in front of it. Being killed by a shark unlocks the "Out Of Your Depth" achievement/trophy.
According to Abigail, a Stranger & Freaks character, sharks in GTA V are "San Andreas White Sharks", a fictional subspecies of the great white shark. They are endangered, hence why they seldom appear in-game.
- Page 10 of the Tourist Guide, GTA Vice City's game manual