If you're talking about 3X a week, all the more reason to share a space.
If you buy a piece of crap boat, you still have to pay for a slip and live on a piece of crap boat. If you buy a nice boat, it will cost a bomb, will depreciate, will cost you 10% a year to maintain if you ever hope to sell it, and still cost you for a slip.
Why not make a friend with a boat and offer to mind it and maybe do some work on it in exchange for staying on it a few nights a week?
If you want a sound investment, stick with real estate. Boating
is for those of us that have already made what we need and want to live in a remote
corner of Panama
as far from Mountain View as possible.