I couldn't find any naval gun I liked on the web, so I found some scraps and threw together this little daisy. She's roughly a 3 1/2 inch gun. I'm going to keep it as a separate piece from the ship, though I may drill a pilot hole in the base of the gun and put a pin on the bow of the ship to keep the gun in place when I place it on the foredeck.
I still need to find some machineguns, though I think I can make my own maxims. I'm starting to think about Lewis guns instead- there are a couple sources for them.