The Water Festival in Pokémon Go celebrates water-type Pokémon, but especially the release of Dewpider and Araquanid into the game.
Throughout this Pokémon Go event, you can collect event-exclusive field research tasks and the Water Festival: Catch Challenge timed research quest.
This event is also an excellent opportunity to complete the A Poni Adventure special research quest and catch Tapu Fini if you haven’t done so already.