Information from the Coast Pilot doesn't sound too promissing:
Charlestown Breachway, 4.5 miles westward of
Matunuck Point, is a narrow inlet which leads to
Ninigret Pond, also known as Charlestown Pond, to
the westward, and the village of Charlestown to the
northward. In 1994, a reported depth of about 1½ feet
could be taken in the inlet, with depths of about 3 to 6
feet inside. The southern part of Ninigret Pond is
mostly mud flats. Local knowledge is required in entering
and moving about inside.
