A Singaporean company has resurrected a post-WW2 German design to commercialize a beautiful reverse-delta ground effect vehicle as a high-speed, high-efficiency ferry for six to eight passengers. The Airfish 8 hovers serenely between two and 23 ft (0.6 to 7 m) over the water and hits speeds of almost 120 mph (193 km/h).
The wing-in-ground effect is well understood at this point: when an aircraft is close to the ground, it operates significantly more efficiently than it does higher up. The additional air pressure underneath the aircraft at altitudes below half the wingspan adds extra lift, and you also get a corresponding reduction in lift-induced drag. The ground effect increases the closer you get to the surface, peaking at an altitude around 5 percent of the wingspan, where you can get a craft operating some 2.3 times as efficiently as if does in free air.
Numerous attempts have been made to capitalize on this effect for quick, efficient transport over water, but right now, the leading players appear to be Sea Wolf Express, which plans to begin a passenger ferry service between Helsinki, Finland and Tallinn, Estonia, using a Russian-built Ground Effect Vehicle (GEV) in 2019, and Wigetworks Private Limited, operating out of Singapore.