This is just science at this point. When combined, ice ends up on top of water. This is just physics.
Melony is able to easily use her size advantage to follow up on her big punch and position herself on top of Nessa- her weight holding her opponent down, and her knees pinning her enemy's hands. Smothered and pinned as she is, Nessa can't easily tap, nor can she verbally submit. That's pretty bad news.