Surf

Surf is a -type move introduced in Generation I. It has been HM03 since Generation I.

In Battle
Surf does damage. If used underwater, Surf will double in power. In a Double Battle, Surf targets all Pokémon around the user, but in Generation III, Surf only targets foes. In a Triple Battle, Surf only targets Pokémon that are adjacent to the user.

Outside of Battle
Surf can be used to travel across ponds, lakes, seas, etc.