Number Sixteen is the ocean beach south of Rye named for the sixteenth of the old back-beach access tracks, and it offers a shallow dive over what The Scuba Doctor describes as a series of low ledges and gullies off the edge of the sea terrace, with interesting undercuts full of fish. The maximum depth is only about 5 m, but the terrain is intricate: the limestone terrace is cut by wave-worn crevices and channels, its seaward edge is undercut into ledges where sweep, old wives, zebrafish, magpie perch, wrasse and leatherjackets crowd, and offshore the reef continues as gutters and low bommies. Weedy seadragons occur in the kelp on the outer reef, Port Jackson sharks rest under the ledges, abalone and the occasional rock lobster are in the holes, and the shallow water gives excellent light for photography.

The site's particular danger is its blowholes: crevices in the terrace connect to the open sea, and the source warns that a freak wave can force a diver through one and against the rocks in a potentially fatal way, so every crevice that pulses with the swell must be avoided. The whole area is very exposed to southerly swell and very calm conditions are required – the usual back-beach prescription of long-period swell under about 1.5–2 m after several days of northerlies, at low tide. Number Sixteen suits experienced divers and strong snorkellers who enjoy shallow, intricate reef and photography on a glassy day; it should never be attempted with any swell running.

From Point Nepean Road in Rye take Canterbury Jetty Road south, continue into Tasman Drive and at the Marcia Avenue intersection turn right into Number Sixteen Access Road; park in the car park at its end. From the car park take the track east to steps that descend to Number Sixteen Beach – a walk of a few hundred metres. Enter and exit from the beach at low tide, when the sea terrace and its gullies are exposed and sheltered.

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 at low tide through a gully, swim out over the sea terrace to the outer ledges in 3–5 m and work along them looking into the undercuts, staying well clear of any crevice that breathes with the swell. Turn at half gas and return through the same gully; the Craigburn wreck lies 370 m to the west-south-west for those with the conditions and gas.

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