Sorrento Back Beach is the best known of the Nepean Peninsula ocean beaches and, because it has a patrolled beach, a large car park and three practical entries, it is the usual first back-beach dive for Peninsula divers. The Scuba Doctor gives a depth range of 2–20 m, the widest of the back-beach shore sites, and describes the underwater terrain of ledges and overhangs that hold crayfish, snapper and, in its words, other lovely edible and photogenic critters, with abalone on the rock. The three entries lead to different diving.

The rock platforms by the headland give access to gullies and reef along the western side; the beach near Darby and Pulpit rocks gives a sand-and-reef mix suited to snorkellers on the flattest days; and the wooden pathway west of the surf club leads to the Sphinx Rock gullies, deep sheltered clefts in the platform that are the most dramatic part of the site and lead out to reef falling away toward 20 m. Everywhere the rock is limestone eroded into caves, undercuts and swim-throughs, roofed with kelp and carpeted beneath with sponges and jewel anemones; the fish are the standard Bass Strait community of sweep, old wives, zebrafish, magpie perch, boarfish and wrasse, with Port Jackson sharks under the ledges, weedy seadragons in the kelp and rock lobsters in the deeper holes. The 1967 loss of Harold Holt at nearby Cheviot Beach is the cautionary tale attached to every description of this coast, and the source's requirement – flat seas, minimal swell, light northerlies, usually after three or four days of north-easterlies – must be respected.

Sorrento Back Beach suits experienced Advanced divers with surf-entry skills, and snorkellers at the beach on glassy low-tide days; it is not a site for the newly certified.

Drive south from Sorrento along Ocean Beach Road for 1.5 km to the large car park and picnic area at the back beach, with the Sorrento Surf Life Saving Club on the bluff. Three entries are used: the rock platforms beside the headland, the beach near Darby Rock and Pulpit Rock, and the wooden pathway west of the surf club that leads to the Sphinx Rock gullies. The beach walk is moderately hard with gear and the route to Sphinx Rock is cut off at high tide, so go at low water.

Exit at the same entry; do not rely on other exits.

The back beaches face south-west into Bass Strait and are safe to dive only in rare flat conditions: The Scuba Doctor's rule of thumb is swell under about 1.5–2 m with periods of 10 seconds or more, usually only after three or four days of northerly to north-easterly winds, with light northerly winds on the day. Any southerly or westerly wind, or a fresh swell, makes the entries lethal. Dive around low tide when the limestone platforms are exposed and the gullies are sheltered, and abort if there is white water over the entry.

Rips and tidal streams near The Rip run even on calm days, and conditions change within an hour. Winter high-pressure systems bring the calmest spells; summer sea breezes rule out afternoons.

At low tide enter via a sheltered gully, swim out through it to the reef edge in 6–10 m and follow the ledges seaward to 15–20 m while watching the surge, then turn at half gas and come back to the gully mouth at 5 m, timing the exit between sets. Keep a fixed landmark on the bluff in sight.

No regular operator. The Scuba Doctor (Rye) and Peninsula clubs run occasional guided shore dives when conditions allow; otherwise experienced private groups only.