Diamond Bay is the most accessible and most snorkelled of the Sorrento back-beach sites, a compact sandy cove between two rocky points with a staircase from a car park at the end of Diamond Bay Road. The Scuba Doctor gives it 1–10 m and Advanced Open Water, and lists the features that make it more than a beach: rock ledges and overhangs, kelp beds, reefs and small walls, bommies, gullies, cave structures and interesting rock formations, deepening toward the points. Underwater the bay is a sand floor rimmed with limestone reef that rises into small walls and bommies at the points, capped with kelp and cut by gullies.

Old wives, boarfish, schooling sweep and zebrafish, wrasse and leatherjackets are constant, crayfish and abalone live in the ledges, and both draughtboard catsharks and Port Jackson sharks rest in the caves; weedy seadragons are seen on the kelp margins. Because the bay is small and enclosed the navigation is simple and the sandy middle offers an easy exit, which is why it is recommended as a first back-beach dive when conditions are perfect; the same sandy bottom, however, means visibility drops quickly when there is any swell, and the points funnel rips. The site is fully exposed to the south-west and the standard requirement applies – flat seas, swell under about 2 m with a long period, light northerly to north-easterly winds, generally after three or four days of northerlies – with an abort if white water is breaking on the reef.

Rock fishers use the points and leave line. Diamond Bay suits experienced divers looking for a manageable introduction to Bass Strait shore diving, snorkellers on glassy days, and photographers after kelp and sharks in bright shallow water.

From Sorrento follow Ocean Beach Road and then Diamond Bay Road to the free car park at its end. The beach is about 130 m from the car, the last 50 m of it a staircase and a beach walk – tiring with gear but the easiest back-beach access. Enter from the sand in the middle of the bay and swim out; the reef and small walls begin close in on either side and deepen toward the points.

Exit back onto the beach. The car park is small and fills quickly in summer.

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.

Enter from the beach, swim out over the sand to 4–5 m and choose a side; follow the reef along the western or eastern point with the rock on one shoulder, exploring the ledges, bommies and caves to 10 m off the point. Turn at half gas, return along the same side slightly shallower and finish over the sand in the bay.

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