Over the course of history, many sea battles have taken place around the world. Seas were not just used to defend or attack another country but were also used to transfer men, equipment, and resources. In the 1940s the United Kingdom Merchant Navy lost many ships and supplies to the German U-boat submarines.
Nations found that controlling the seas could mean controlling the import and export of goods, and with that they could control money, taxes, and resources in a particular region.
With the different types of technology available through history there are many things that you could do in your own games to have a different slant on your war games.
As well as the traditional ships such as battleships and destroyers, ...