Surface effect ship A Surface Effect Ship ( SES ) or Sidewall Hovercraft is a watercraft that has both an air cushion , like a hovercraft , and twin hulls , like a catamaran . When the air cushion is in use , a small portion of the twin hulls remain in the water . When the air cushion is turned off ( " off - cushion " or " hull borne " ) , the full weight of the vessel is supported by the buoyancy of the twin hulls . The SES has two advantages over a hovercraft for open sea operation : it is more resistant to slipping sideways when acted on by air or sea and , and it can use water jets for propulsion since the inlet nozzles are always covered by water . United States Navy . The United States Navy initiated the SES model test program in 1960 . By 1963 , a 10 - ton test craft called the XR - 1 was designed and built to test the surface effect concept . The first version of the XR - 1 used fixed plywood seals at the fore and aft ends of the captured air bubble section . A jet engine providing 1700 pounds of thrust was used for main propulsion . A separate gas engine was used to drive lift fans , and also to power out - drive units that were used for off - cushion slow - speed maneuvering . During the first year of testing , the XR - 1 was fitted with more powerful main propulsion and flexible fore and aft seals were tested as well . The XR - 1 was also used to test the concept of water - jet propulsion . The ship was modified in 1964 and equipped with gas turbine engines driving the water jet propulsors . The ship ' s weight increased to 17 tons . Rohr Industries 1970 to 1980 . Rohr Industries became involved in SES history in 1970 , taking over the XR - 1 test program for the Navy . Rohr continued to use the XR - 1 to test propulsion and seal concepts . Their eventual goal was to develop a 3000 ton SES capable of utilizing vertical launch missile systems and anti - submarine helicopters . The proposed ship was to be capable of 80 knots in sea - state 6 conditions . The proposed main power units were to be 4 40 , 000 hp gas turbine engines driving water jet propulsors . The 3000 ton ship development contract was canceled in 1980 . The SES100 . Two experimental SESs ( the SES100A and 100B ) , both of around 100 tons , with 80 ft ( 24 m ) length and 40 ft ( 12 m ) beams , were developed for the US Military in the 1960s and 70s . They both attained speeds in excess of the program goal of 80 knots ( 150 km / h ) . The SES 100B , was built by Bell Aerospace ( Textron Corporation ) at the NASA Michoud Assembly Facility . Driven by 2 semi - submerged , supercavitating controllable , reversible propellers , achieved speeds in excess of 96 knots ( approximately 110 mph ) in the Gulf outside of St . Andrews Bay in Panama City , Florida . The speed was verified by the USAF ARIS radar . It also fired the Navy ' s first vertically launched missile ( an SM - 2 ) while doing 60 knots ( 110 km / h ) . It was also used to test automatic ride control and high speed collision avoidance and navigation systems . The 100A ship was used to test waterjet propulsion , variable geometry inlets and automatic ride control systems . The 100A and 100B were both capable of operating almost completely out of the water on an air cushion with only 18in ( 46 cm ) of sidewall , the propellers or the waterjet inlets entering the water . The 100 ton SES 100B was built for the US Navy as a 1 / 10 scale model to test the feasibility of using hovercraft and other Surface Effect Ships in combat situations . The top - secret specifications called for a ship capable of entering a combat zone at a speed of over 80 knots ( 150 km / h ) and disgorging a tank and 100 soldiers onto a beach , turning back out onto water and escaping at high speed . Unlike the hard sidewall SES ' s , the full skirted AALCs , JEFF A & B were the prototype vehicles for the LCAC ' s used by the Navy with such success in the Persian Gulf War . The 3000 ton SES concept was never designed to go up on the beach , like a landing craft . The AALC ( Amphibious Assault Landing Craft ) and the SES were very different concepts from the beginning . The AALC was a pure hovercraft that is capable of high speed insertion of troops and vehicles onto a beach . As a hovercraft , the LCAC , derived from the AALC has no rigid hull parts that extend past the air cushion . It therefore can operate across the beach . The SES has rigid side hulls that enclose the air cushion , permitting water propulsion but allowing it to only go to the shore when conducting amphibious operations . Design concepts for a 6000 + ton cargo SES ' s that Rohr and Ingalls Shipbuilding proposed relied on the idea of the ship loading and unloading from beach , lighter , causeway or conventional dock facilities . Hovermarine SES Ferries . The UK based company Hovermarine developed the HM . 2 SES ferry at their factory in Woolston , Southampton in the 1960s . The first HM - 2 craft was operated by Seaspeed in 1968 between Ryde Pier and Portsmouth Harbour . The early HM2 suffered from mechanical problems and during a financial crisis in 1969 , Hovermarine went into voluntary liquidation and the major assets were acquired by a new company , Hovermarine Transport Ltd , this was subsequently taken over by the American company , Transportation Technology Inc . Production of HM . 2s for North and Central America was undertaken by Hovermarine ' s factory at Titusville , Florida . Over 110 HM . 2 ' s were manufactured in the UK and US Operational use . Currently SESs are used , primarily as small ferries . The Soviet Navy built two 1050 ton Bora class surface effect corvette s . The ships were passed on to the Russian Navy and remain in active service with the Black Sea Fleet . The Royal Norwegian Navy built 9 Alta and Oksøy class surface effect vessels for mine warfare . The Norwegian Navy also operates six Skjold class surface effect patrol boats . These ships are the fastest warships in the world with service speeds of . The prototype ( KNM Skjold ) was leased and tested for one year by the US Navy .