Mount Sinai Harbor is located three miles west of Port Jefferson and is 16 miles to the southeast of Bridgeport, CT, across Long Island Sound. Mount Sinai was not always the relatively deep, well protected harbor it is today. A long time ago, there was little more than marsh and mud as far as the eye could see, but eventually the area was dredged to become what is now a first class stopover on Long Islands North Shore.
In addition to the four marinas and large mooring field here, there is a fine sandy beach (Cedar Beach) that is popular with visitors on the Long Island side of the harbors edge. All the marinas and boatyards in Mount Sinai Harbor accept transient guests at their slips, and a large mooring field is available for those whod rather sit on a mooring for the evening. There is limited anchorage at the east end of the harbor, but the holding is unreliable. If you anchor here, make doubly sure that your hook is set.
Use NOAA Chart 12362.
From Long Island Sound, pick up red and white buoy M just north of the inlet to Mount Sinai Harbor. Two breakwaters border the east wand west sides of the inlet, and the outer ends are marked with a flashing red and flashing green light (unnumbered).
Once inside the breakwaters, the channel will shallow, and then you will begin to make a sharp turn to the east. As you move farther in, be aware of a small shoal that protrudes toward the channel from the Cedar Beach side of the channel, where depths shallow to two feet. Once you have completed the turn, a series of privately maintained aids to navigation (nun buoys) will lead up the harbor. Twelve to 13-foot depths skirt right up to the marinas on Cedar Beach and farther east toward the head of the harbor.