High-speed Sea Service or Stena HSS was a class of high-speed craft developed by and originally operated by Stena Line on European international ferry routes. The HSS 1500 had an in-service speed of 40 knots (75 km/h). Several patents were registered to Stena Line in the development of the HSS, and four vessels were completed between 1996 and 1997. Stena Explorer, Stena Voyager and Stena Discovery were built to operate on the Irish Sea with Stena Carisma built for Scandinavian use. The newest of the craft was renamed HSS Discovery after being sold to a ferry company in Venezuela during 2009.