Meaning : 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.
Example :
The fins of a fish act as hydrofoils.
Synonyms : foil
Meaning : A speedboat that is equipped with winglike structures that lift it so that it skims the water at high speeds.
Example :
The museum houses a replica of the jet hydroplane that broke the record.
Synonyms : hydroplane