As I've researched it a bit, it's more like leasing than owning, only different
The average unlimited boating plan with a major club was around $5k per year. And that gives you some choices when you travel. If you think you're going to get something akin to a rental, stay renting.
It's a great plan for someone that doesn't want the hassle of winterizing, etc. But they come with monthly costs, every month usually.
Not a bad idea, if it fits your idea.