Captain Peter Fraser (Brian Reece) is in town as he is due to take command of the HMS Sherwood in the morning but he finds himself bumping into an old friend, Tom Baker (David Tomlinson - The Way to the Stars) who is a secretary for the Admiralty. As they decide to have a drink one leads to another and another before they know it they are not only drunk but have swapped clothes and rooms. Come the next day Tom is mistaken for Peter and before he knows it finds himself aboard the battleship whilst Peter finds himself having to do Tom's job.
Not to be confused with the more famous Carry On movies which started in the following year "Carry on Admiral" is one of those typical British confusion comedies. These movies were ten a penny during the 50s and for a confusion comedy it is a simple affair as Peter and Tom find themselves being mistaken for each other and having to try and keep things together especially Tom who is no sailor. There is also another bit of typical confusion as early on Peter tries to charm a pretty young woman whilst making harsh judgements of old Admirals unaware that she is the grand daughter of Admiral Sir Maximillian Godfrey.
The trouble is with "Carry on Admiral" and probably explains why it is not that well known it that it isn't really funny. Oh it is full of jokes from an early scene of marching sailors falling over each other when they spot a pretty woman to the comedy of Joan Sims as a housemaid in the hotel dealing with a drunk Tom and Peter. But none of the humour is either memorable or laugh out loud funny, just the same sort of gags and ideas which filled these 1950s British comedies.
What that does mean is that now "Carry on Admiral" is more entertaining for who is in it. David Tomlinson is amusing as Tom Baker as he struggles with a hangover aboard a ship whilst Joan Sims is fun as Mary the housemaid; in fact Sims has the funniest scene where she is telling Tom all about the room numbers. Aside from that well there is not much to say except that Eunice Gayson is eye catching as Jane Godfrey especially during the overboard scene but that is it.
What this all boils down to is that "Carry on Admiral" is a typical but forgettable British farce from the 1950's whose appeal now is more to do with who is in it rather than the actual movie itself.