These were some of the cutting edge naval propulsion technologies available or plausibly available around the time period, suitable for making very fast torpedo crafts, weren't developed for military use in the real world, but were plausibly available to build had the need to do so not been superseded by aviation. Hoping to see these in game to ruin a battleship's day, particularly in the possible absence of airplanes.
Hydrofoil, 35kn in 1909! Imagine That!
Ground Effect, this one is technically a plane though.
Air Cushion, 70 knots in 1930!