[aerohead]

There used to be something called 'lamniflow' technology, but I can't find it online. I believe it was tested on torpedoes.
Riblet technology has been explored, derived from shark skin. Pockets of dead water are captured all over the submerged surface, and surrounding water touches mostly water on the Hull's surface.
The Russians use 'bubbler' technology, which introduces a layer of air bubbles along the hull's surface, reducing the amount of fluid actually in contact with the hull.
An extreme case is, the rocket-powered Russian torpedo, which shunts a portion of the rocket exhaust to the nose, and the torpedo travels as a full-cavitation device, never actually in contact with the water.
Other than all that, the other strategy is to raise the hull onto hydrofoils, lifting most of its surface completely clear of the water.