Back in the 70s, the US Navy was serious about a hi-lo mix of surface combatants. The Lo end was going to be filled by the Pegasus-class. These were intended for use in the Mediterranean and Baltic seas, basically a small, near-shore counter to Soviet fast attack craft.
Enter the Pegasus-class. These were small (about 250 ton) hydrofoils. Being hydrofoils, they have wings on struts that lift the hull out of the water at speed, significantly reducing drag. As a result, the Pegasuses could make over 48 knots in calm seas, and over 40 knots in rough seas. Power was an LM2500 gas turbine when foilborne, and a pair of diesels when hullborne. This was fantastic in the 1970s, and is still impressive today.
Armament consisted of the ubiquitous 76mm Oto Melara gun, plus two quad harpoon launchers in the US Navy versions. The proposed versions for the German Navy had a pair of quad Exocet launchers.
Changing priorities saw Italy cancel their order, the US Navy drastically reduce their order, and then the Germans cancel their order. The remaining Pegasuses had a happy and successful life in coastal jobs, including running down drug smugglers.
So what do we think? Speed is fun. I think the concept has merit in the fast attack space, but it would be a pain to deploy without good forward basing. There was also a mothership proposed to assist in deployments but that was also cancelled. Overall though, while tricky to deploy for the US Navy, they’ve got a lot of merit for allies looking for relatively low cost punch.