All marinas will shut off water and pump outs in the winter. The question is are there heated locker rooms with showers and restrooms that are open year round, do they have bubblers, and are they going to freak out about a liveaboard who's running an electric heater to keep his boat warm while he's at work.
You also have to contend with the weather. It seems like we've been averaging two nor' easters a month. If you're on the coast, or even on Barnegat Bay that means 50-60mph winds and six foot tidal surges.
FWIW, that long cold walk up the dock for your morning shower when it's 20 degrees and the wind is howling off the water is not for the faint of heart.
Even without all this winter's storms I wouldn't recommend it in this part of the country.
Just My 2 Cents,