Hydrofoils and hovercraft are totally different types of vehicles.
The hydrofoil raises the bow on wings, so there is still physical contact with the water.
The hovercraft is above the water on a cushion of air.
The Navy ran hydrofoil ships, Pegasus class, from the late 70's to the 90's. They were eventually evaluated as failures due to complex mechanical maintenance and that the foil leading edges were being destroyed by cavitation.
Both the hydrofoil and hovercraft for commercial transportation were surpassed by the double hull catamaran because the catamaran uses less fuel for the payload and provides a more stable ride.
The Superferry came from an Australian company that was already building them for other markets. For near shore interisland, they are fast enough and stable enough, in areas of high density population, to be profitable.
It would take too long to describe the history of the Superferry to where it is now, the two that were built are in Navy service (JHSV), but if you look at the Austal page, both Austal and the Navy have moved on to trimaran, after finding the limits of catamaran.
http://www.austal.com/us/Home.aspx
Doesn't mean there is a snowball's chance in Kau of another private sector superferry in Hawaii. Hawaii is not near shore, not high density population, and the ocean conditions change rapidly around these islands.
"This island Hawaii on this island Earth"
