When checking the toy isles at supermarkets, Wal-Mart, Target, even drug stores and liquor stores, sometimes I run across an interesting vehicle or boat.
Over the years I have found a few sailboats, mini submarines and other toy items that look good in marinas all around the world for the last 50 years.
Small cabin cruisers can be converted to patrol boats, these two white ones are from Athern the model train company. I painted a third one in US Army markings and decalled to too. The US Army used dozens of these kinds of boats in WWII for mine tending, sub nets, and patrol work.
Small submarines can be used for recon, sabotage, and landing a couple troops too. Caesar Miniatures in their recent Special Forces set has several frogmen figures.