After building all those Revell Type VII U-Boats I had five hulls left over, since I waterlined the models, I had the lower hulls in the spares box. They are a big honking bit of plastic and too good to just toss away. So I am using them. I made a U-Boat interior based on one of them. I made a pre-WWI "fantasy" submarine out of one and will probably do a second one of those. I plated over the bottom opening on one and use it in conjunction with one of the U-Boats to create a temporary full hull version if I need one out of the water for repairs. My final U-Boat hull will be used to make a US Navy ship. Here is part of the work already done.
These little guns have been in the spares box for at least ten years, the beads at least five. The little building is a guard shack from some WWII German set, maybe Nitto. It will become the bridge.
The main gun is a US Army 155 M-12 gun taken from perhaps an Esci M-12 kit long ago. It will probably be given some kind of gun shield.