https://www.youtube.com/watch?v=BlTibownuTQ
Supercavitation encloses a hull or strut in a gas bubble so most of the wetted surface never touches liquid water — drag can fall by orders of magnitude versus a fully submerged body.
Craft such as Juliet Marine’s GHOST ride on supercavitating foils: gas injected or vaporized at the leading edge sustains the cavity, enabling high speed with much less hull friction.