This is called the
#pumpfoil. She is
#pumpfoilingYou pump up and down with your legs and that motion alone is all that is necessary to translate via a hydrofoil under the water surface (like a wing) to give you lift and forward motion
You need good balance, endurance, and if you stop pumping you lose lift and sink rapidly
EDIT: this is Alina Kornelli. See
@bruno 's comment below
EDITEDIT:
https://youtube.com/@alinakornelli
