As a Slime, Suu's true form is a large mass of a transparent blue gelatinous slime. She also has a mass of green "hair" with three yellow "antenna" on the tips. For easier interaction with humans, Suu shapes herself into a somewhat humanoid form that, according to Miia and Centorea, is unheard of for a Slime to be able to do. Suu normally shapes herself to be about the same size and build as Papi, but when she absorbs a certain amount of water, she chooses a more mature form: she becomes taller, bouncier, and curvier than usual. The excess water goes straight to her bust and hips. When dehydrated enough, she becomes small enough to fit into a small bucket -- showing as only a head and hands peeping over the rim.