With only the two entries I can now announce the winner as David.
The runner up was Bill.

There are actually no fewer than 11 out of the 12 OPERETTAS WITH MENTIONS OF THE SEA OR SAILORS.

As stated Pinafore and Pirates go without saying, so I did not count those in the tally.

Mikado as David says has the Nanki Poo song Wandering Minstrel with the verse beginning If you wish for a song of the sea.

The Gondoliers has the Duke of Plazatoro singing that if ever he gets back to Spain he will never cross the sea again.

Patience contains Colonel Caverley's Heavy Dragoon song with reference to Victory and the pluck of Lord Nelson devising a plan.

Princess Ida opens with the song " Search through Panorama for a sign of Royal Gama who today should cross the water with his fascinating daughter.

The Grand Duke. Has the Prince of Monte Carlo from "Mediterranean water."

Iolanthe, the Chancellor's nightmare song “and you dream you are crossing the Chanel and tossing about in a Steamer from Harwich”.

In the Yeomen of the Guard, Wilfred Shadbolt Jack Point sing of Colonel Fairfax escaping to the shipping.

In Ruddigore we have Dick Dauntless a Man’o Wars man sing his song "The revenue Sloop."

The Sorcerer, apart from Alexis mentioning that he is a member of the Army and Navy Stores, contains John Wellington Wells singing of his engagement to a maiden fair who waits for me by the sounding sea on a South Pacific isle.

Finally as David so rightly states in Utopia limited there is mention of Sir Edward Corcoran of the Royal Navy.

Well done chaps.

Rob.