hy·dro·foil /ˈhaɪdrəˌfɔɪl/
  水中舵
  hydrofoil
       n 1: a device consisting of a flat or curved piece (as a metal
            plate) so that its surface reacts to the water it is
            passing through; "the fins of a fish act as hydrofoils"
            [syn: foil]
       2: a speedboat that is equipped with hydrofoils that lift it so
          that it skims the water at high speeds; "the museum houses
          a replica of the jet hydroplane that broke the record"
          [syn: hydroplane]