I'm guessing this film takes place in the 1950's. Young English sailors are building and sailing 12' Fireflys, an Uffa Fox design. The Firefly is still raced today in England and is the team racing dinghy for English Universities. I enjoy watching old film and this has the typical "jolly good... hip hip hooray" narration of English shorts of this period.
My good friend, Bob Blomquist, raced in a small fleet of Fireflys in and around Boston Massachusetts during the1950's.