Nepean Bay Inner East, known as Radar for the old radar station that stands on the hill directly above it, is one of two shallow reef patches on the inside of Point Nepean that the Parks Victoria divers' guide singles out, and which the Scuba Doctor listing reproduces. It lies midway along Nepean Bay in 1–5 m, and is rated for snorkelling, Open Water and beyond – a site for looking closely rather than going anywhere.

The reef is a low ledge system covered in kelp, and the listing's summary of its appeal is precise: 'a large variety of fish species' and colourful nudibranchs concealed among the kelp. Under the fronds and in the gutters are the small animals of a protected shallow reef – nudibranchs of several species, sea stars, decorator crabs, small crayfish – and over it the fish that have multiplied since the marine national park closed the point to fishing: scalyfin defending their patches, old wives in pairs, moonlighters, wrasse, leatherjackets and juvenile sweep. Rays lie on the sand at the reef edge and cuttlefish use the ledges in winter.

Like its neighbour Inner West it is exposed to the tide despite the shelter of the bay and is best dived on the ebb. It is entirely a boat site: the shore is national park and landing or shore diving from Point Nepean is prohibited. For snorkellers it is among the best shallow water at the Heads, clear and calm on a northerly-free day, and for photographers it is a macro site to work on hands and knees in a metre or two of water. Radar and Inner West are usually visited on the same trip, with the boat moving 270 m between them.

Boat access only – Point Nepean is a national park and the listing notes that shore diving is prohibited from the point. Charters from Portsea Pier (Dive Victoria Group, Bayplay) are 5–10 minutes west along the shore; Red Boats from Queenscliff about 15 minutes across the entrance. Private boats launch at Sorrento Boat Ramp (Point Nepean Road, all-tide, trailer parking) and run 15 minutes west past Portsea.

Nepean Bay is shallow and the boat anchors on sand outside the reef line or holds off; a dive flag is required and the pilot boats and ferry pass close to the bay. The radar station building on the hill above is the landmark for this patch.

Nepean Bay is 'sheltered from all winds except northerlies' (Scuba Doctor) and is the standard fallback when the Heads are unworkable, but the tide still runs through it: the Parks Victoria guide advises diving these reefs on the ebb, when the outgoing tide leaves the bay in relatively still water and any drift sets back toward Portsea rather than out through the entrance. Slack water at Port Phillip Heads does not coincide with high or low water: it falls roughly three hours after high or low water at Point Lonsdale, and the usable window is typically 20–40 minutes. Use the Ports Victoria / Port of Melbourne slack-water predictions for The Heads (also republished by charter operators and WillyWeather 'Rip Bank') rather than a standard tide table.

A northerly over about 15 knots puts a chop on the bay and cuts visibility; swell has little effect. Diveable year-round; clearest in autumn. Water 12–13 °C in winter, 17–19 °C in late summer.

Anchor on sand off the reef on the ebb and snorkel or dive over the kelp-covered ledges at 1–5 m, working slowly and looking into the kelp for nudibranchs and under ledges for crayfish; return to the boat along the reef edge.

Dive Victoria Group and Bayplay (Portsea) as a snorkel or shallow second dive; Sea All Dolphin Swims and Polperro snorkel tours visit Nepean Bay; private boats from Sorrento.