Fiddler: Malcolm Webster and Pam Barfield(of Steamhead) had a real piano on their narrow-boat Mallard. Very good for parties. They've changed boats now, but alas there's no piano in the new one.
When I was on the boats we built a high cross cross-bed up at the sharp end just below gunwale height(to tuck my feet under), and managed a lot of instrument storage in two layers underneath the bed.