Water is the most common hazard and obstacle in the Pikmin series, since it is presented mostly through bodies of water that are a part of the terrain itself. Water is a hazard to most Pikmin types, given that they cannot swim nor breathe underwater. The exceptions are Blue Pikmin and Bulbmin, making these two types of Pikmin ideal to handle underwater tasks. Winged Pikmin can also fly above the surface, making it possible to transverse bodies of water with them in the group.
Water in and of itself is not harmful to the Pikmin. Some bodies may be too shallow for the Pikmin to drown in, in which case they are completely harmless. Geysers also spew out water with immense force, but the Pikmin simply ride them in order to leave the cave. Rain in Pikmin 3 also has no adverse effect on the Pikmin.
In Pikmin and Pikmin 2, leaders, Blue Pikmin, and Bulbmin stick to the bottom of the terrain while underwater, and gravity acts as if they were on land. In Pikmin 3, Blue Pikmin were given the ability to swim, allowing them freedom to move up and down, such as when chasing aquatic enemies. Leaders will always remain on the ground, however, and when they throw a Blue Pikmin, said Pikmin will slowly ascend and descend while underwater.