I usually mount mine in acrylic gel to simulate a seascape. Once it hardens, the model is in there for good.
You can also attach the model to a wooden base with acrylic gel, but not in a seascape, by using the gel as a glue to hold the model to the base. Again, once it's attached - it's pretty much forever.
The trick here is to keep the gel under the hull, so it doesn't show.