Blue Pikmin

Blue Pikmin are resistant to water. They have gill-like ducts which are their mouth to distingulish from other pikmin.

Pikipedia Wiki Data
The links will go to the pikipedia.

Blue Pikmin are distinguishable from other Pikmin by their pink gills, resembling a mouth. Producing more can be done by returning objects to the Blue Onion or using Lapis Lazuli Candypop Buds.

Only they and Bulbmin are able to safely traverse watery areas; any other color will only flail around in panic before drowning. They are able to perform any action inwater that they can on land. If they are idle and see a nearby fellow Pikmin drowning in water, they will quickly run to them, pick them up, and throw them to shore. However, be sure to know when to call the Pikmin, and when to let the blues go for them; often whistling to them will suffice, but if they fell off a ledge, then the blues will carry them to the other, more shallow shore, which might be too far away for the drowning Pikmin to "swim". Blue Pikmin in Pikmin 2.Blue Pikmin are the last color of Pikmin discovered in both games. In Pikmin, their Onion is found in the Forest Navel, and in Pikmin 2, 5 blues can be found near their Onion in Awakening Wood by the use of Yellow Pikmin. Yellow Pikmin are required to break down the electric fence: throw them up onto the ledge, then run around, through the water, to whistle them. There is a Cloaking Burrow-nitburied there that must be defeated. Blue Pikmin seem to be well-balanced in strength, mobility, and throw. They are often considered the most useful Pikmin, especially in Pikmin, because they can go in water, which takes up a large amount of the terrain.

Blue Pikmin are statistically more likely to be eaten by an enemy than any other type. From this, it might be concluded that their color is the most attractive to beasts, that they are in some way the tastiest, or that they cannot evade being eaten as well as other Pikmin.