The Navy experimented with double hulled ships in the late 1970's and early '80's; the space between the hulls was hollow and high-pressure air was pumped into the space. Small holes in the outer hull would allow bubbles to escape and flow around the hull, thus "lubricating" the hull/water interface and reducing friction. This had a two-fold effect - increasing speed and/or reducing fuel consumption.
The big drawback was increased hull noise as the bubbles surfaced and the compressor noise was detectable.
Hard to believe they would be stupid enough to try it. Bubbles are real bad if you are trying to be quiet.
