The area from Great Captain Island southwestward is fringed with rocks, bare and submerged, and foul ground. Great Captain Rocks, part of a reef 0.3 mile southeastward of Port Chester Light 4, uncover 5 to 6 feet; a buoy marks the southern end of the reef. Transport Rock, about 0.3 mile south-southwestward of Manursing Island, is part of several ledges generally bare at high water that extend some 0.3 mile offshore. An opening suitable for small craft leads to Rye Beach; it is buoyed.

Playland, a recreational center at Rye Beach, about 2.4 miles southwest of Great Captain Island, has prominent twin towers at the entrance that are conspicuous from a southeasterly direction. Westward and close to the north breakwater is a former ferry landing in disrepair. A breakwater extends eastward from the south end of Rye Beach. The area between the former ferry landing and the south breakwater is reserved for swimming.

Forbes Rocks, about 0.4 mile south of the Rye Beach breakwater, are partly bare at low water, on a reef with depths of 4 to 11 feet that extends 250 yards to the southward and eastward. A buoy marks the east end of the reef. A channel good for a depth of 9 feet leads southward of buoyed Forlies Rocks to the ruins of a wharf at Oakland Beach. Another channel with a least depth of 8 feet leads southward from Oakland Beach to the sound.

Porgy Shoal, about 0.8 mile south of the Rye Beach breakwater, has a least found depth of 5 feet; it is marked by a lighted buoy.

Scotch Caps are three rocky islets 1.4 miles southwestward from Porgy Shoal and on the northwest side of the extensive reefs that make out 0.9 mile southwestward of Milton Point. The southerly end of the reefs is marked by a lighted bell buoy about 0.6 mile southward of Scotch Caps. The entire area of the reef northward and northeastward of the lighted bell buoy is very broken and should be avoided even by small craft in the absence of local knowledge.

West Rock, just south of the south end of Scotch Caps, is marked by a buoy.

Milton Harbor, between Peningo Neck and Hen Island, is used as a summer anchorage by small pleasure craft. It is protected from all but southwesterly winds. The harbor depths decrease from 8 feet between Scotch Caps and the southwest end of Hen Island to 6 feet abreast Milton Point.

Foul ground is on the northwest side near Hen Island; otherwise the principal danger in the harbor is a rock bare at low water and marked by a buoy a little northward of midway between Milton Point and the northeast end of Hen Island. The best entrance is between the buoys 0.4 mile southwestward of Scotch Caps.

A yacht club and landing are near the southwest end of Milton Point. Near the clubhouse is a prominent white flagstaff from which lights are exhibited from sunset to sunrise during the summer.

A dredged channel, marked by buoys, leads through the harbor from about 400 yards northward of Milton Point to the city boat basin and marina below Mill Pond. Two boatyards are in the harbor. The largest marine railway can handle craft up to 40 feet in length; gasoline, water, ice, marine supplies, and complete engine and hull repairs are available. The city harbormaster is at the boat basin.