Pine Island Bay is in Groton at the mouth of the Thames river (next to UConn). So a long way from Mystic.
With your
draft, you should be able to go up the Mystic river, through the drawbridge and
anchor in the shallow flats anywhere you want. If you don't want to wait for the drawbridge (once an hour during the daylight), you should be able to
anchor anywhere you want south of the railroad bridge and
dinghy 1/2 mile up river to the downtown
dinghy dock. Your draft gives you many options.
Mark