Re: Marinas in Manhattan
Yes, there are a few that I've found in the area but they're all pretty expensive. The one in Chelsea Piers is good and they allow transient dockage but I recall the cost being something like $7/ft or something like that. But it's not a bad place to dock, go bowling at the lanes and grab something to eat at their microbrewery.
I also found a place down in Battery Park but that's also pretty expensive. One thing I thought was funny was that they allow you to 'stop' there for 15 minutes for $1/ft. So I guess it's good if you want to stop, grab a sandwich to go or to pick someone up...
Other than that, I'm still looking myself but there's not much.
Oh, and regarding Chelsea Piers, I think you have to call MarineMax for more info. Good luck.