Weresharks are, obviously, a breed of therianthrope where you have a human who turns into a shark. Despite the general lack of popularity of aquatic adventurers and monsters, they've got a long appearance in Dungeons & Dragons (with inevitable Pathfinder counterparts), and even Werewolf: The Apocalypse has them.
Largely associated with the Forgotten Realms and Ravenloft settings, and specifically the sahuagin race. The sahuagin splatbook "The Sea Devils" has an alternative wereshark which is basically its version of the wolfwere.
Appear in Pathfinder, and even have a skinwalker lineage related to them.
World of Darkness
They're called Rokea and are almost always born to female sharks, generally having very little to do with the human world.
|The Therianthropes of Dungeons & Dragons|
|Laridian - Loup-garou - Loup du Noir - Lythari - Red Falcon - Seawolf - Selkie - Shifter - Swanmay - Thebestyn - Vodoni - Werebaboon - Werebadger - Werebat - Werebear - Wereboar - Werecat - Werecrocodile - Werefox - Werehyena - Werejackal - Werejaguar - Wereleopard - Werelion - Werepanther - Wererat - Wereraven - Wereray - Wereseal - Weresnake - Wereshark - Werespider - Wereswine - Weretiger - Werewolf|
|Antherions: Aranea - Song Dragon - Jackalwere - Wolfwere|
|Third Party: Werealligator - Wereanaconda - Werebunny - Werecheetah - Werecobra - Weremustela - Werepossum - Wereraccoon - Werestag - Werewolverine|