Portsea Pier East Reef is the natural reef that lies under the boat moorings of Weeroona Bay, immediately east of Portsea Pier and running toward Point Franklin, to a depth of about 11 m. The Scuba Doctor lists it separately from the pier and from Portsea Cray Reef 190 m to the west, and describes it as a reef system that stretches beneath the moorings with young fish and small critters – a nursery reef in clean, tide-flushed water where juvenile leatherjackets, wrasse, sweep and old wives school among the kelp and seagrass, and the ledges hold decorator crabs, octopus, nudibranchs, sea hares and the blue-ringed octopus that Portsea is known for. Weedy seadragons move between the pier's kelp beds and the reef, fiddler rays and stingarees settle on the sand patches, and the mooring blocks and chains add small artificial reefs of their own, thick with sponge and ascidian growth.

The reef is the connecting tissue of the Portsea shore-diving complex: from the pier a diver can cross it to the cray reef or to Point Franklin, and it is the middle section of the three-part dive the source describes from Point Franklin. On its own it is a comfortable Open Water dive with more depth than the pier, but its exposure to tide and to boat traffic overhead lifts it into intermediate territory – the source is emphatic about never swimming on the surface inside the pier, always towing a flag, and diving only on south-westerly conditions. Visibility is typically better than at the piers further east because Bass Strait water floods past on every tide.

It suits divers who have done Portsea Pier several times and want natural reef and depth without a boat, photographers after juvenile fish and macro subjects in good light, and anyone planning the longer Point Franklin traverse.

Park near Portsea Pier on Point Nepean Road (free after 6 pm; 1–2 hour limits by day in summer; unrestricted May–November) and walk to the beach on the eastern side of the pier root, about 50 m. Enter from the sand and swim east and out under the moorings, or enter from the pier's lower landing about halfway out and swim east. Never surface-swim inside the pier where boats berth.

Exit onto the beach east of the pier or at the lower-landing ladder.

The Scuba Doctor lists this reef as diveable only on south-westerly conditions – offshore winds that keep Weeroona Bay flat – because it lies outside the pier's shelter and northerly or north-westerly winds chop it up and cloud the water. It feels the tide more than the pier: plan for slack water and expect to be set east toward Point Franklin on the flood and west toward the pier on the ebb. Summer boat traffic to and from the moorings overhead is heavy, so early morning, evening and winter are the sensible times, and a towed flag is mandatory.

Enter from the beach east of the pier at slack water, descend in 2–3 m and work east and seaward under the moorings across the reef to 9–11 m, using the mooring blocks as waypoints. Turn at half gas, return along a shallower line at 4–6 m toward the pier, and exit at the lower landing or the beach; carry an SMB in case the tide takes you toward Point Franklin.

Bayplay (Portsea) guides include it in extended Portsea Pier dives; otherwise independent divers who know the pier. No charter needed.