Swoopin' Stus are the small, blob-like creatures in Super Mario Sunshine. These creatures come out of goop, whether the area of goop is big or incredibly small. They are first seen during the battle with the Goop Piranha Plant on the Airstrip. Swoopin' Stu's can appear in various colors. Swoopin' Stu's eventually jump into the air, and on to the ground, dooming themselves.
The only real way Swoopin' Stus can harm Mario is by jumping into him. They sound with a "boww wop" noise and then pounce at Mario. Swoopin' Stus also create trails of goop when they move along. Swoopin' Stus can be eliminated simply by squirting water at them with F.L.U.D.D., or by jumping on them, which sometimes, if Mario's water tank is low enough, releases packs of water to refill F.L.U.D.D..
Swoopin' Stus used to have a wider bottom, no head tentacles, and they did not make any sound. They did not even turn white to let Mario know they were pouncing.