I Saw Three Ships (Come Sailing In)" is a traditional and popular Christmas carol from England. The earliest published version of "I Saw Three Ships" is from the 17th century, possibly Derbyshire, and was later printed by William Sandys in 1833.
The lyrics mention the ships sailing into Bethlehem, but the nearest body of water is the Dead Sea about 20 miles away. The reference to three ships is believed to from the three ships that carried the relics of the Biblical magi to Cologne Cathedral in the 12th century. Another possible reference is to Wenceslaus II, King of Bohemia, who bore a coat of arms "Azure three galleys argent". Another suggestion is that the ships are actually the camels used by the Magi, as camels are commonly referred to as "ships of the desert".
No matter how we might explain three ships getting to Bethlehem, we see the point of the carol is to praise the arrival of the new king
"And all the bells on Earth shall ring,
On Christmas Day, on Christmas Day".
Bells ringing out was often the way many cultures would announce the arrival of a royal baby.