Medusal Slurker

The Medusal Slurker is an enemy introduced in Pikmin 3. It is a floating, translucent jellyfish-like enemy that is a member of the Umbloda Family. It has a green pouch inside its head to store the food it eat. This pouch can be extended to the ground to trap Pikmin (species) and Captains. It is first fought in the Garden of Hope, as defeating it will allow you to discover the Rock Pikmin it had in its body.

Pikmin 3 website
"These gelatinous creatures float above their prey and suck them up into their transparent bodies."

Trivia

 * It was the first new enemy fightable in the E3 2012 demo.