Marinas that can accommodate a group on the south shore is a tough one to find they fill every weekend and many of them are town marina's so out of towners in the height of the the season just doesn't happen. To top that off Watch hill is closed this summer for a refit so its going to be hell trying to get a slip anywhere on the south shore this summer.
This is why I went east 16 years ago it the best place to boat.
I did the city a few years ago so not ready to go West again you need about 10 years to get over it
It was a great time but we are just Spoiled and use to less congestion