noun (n)

• 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(noun.artifact)

  Example:
  The fins of a fish act as hydrofoils.
  

  Synonym:
  foil
  

  source: wordnet30
• a speedboat that is equipped with winglike structures that lift it so that it skims the water at high speeds(noun.artifact)

  Synonym:
  hydroplane
  

  source: wordnet30