The Lee Breakwater is the long rock wall that forms the northern arm of Portland Harbour, running east-west for 1,179 m from the foreshore below the town, and its outer face is Portland's shore dive. The Scuba Doctor describes a rocky wall with abundant seaweed cover that is a good night diving site and one where beginners cannot get disorientated, because the wall is always there to follow home. The dive runs from Nuns Beach along the northern side of the breakwater down to the pump house and wave marker about halfway along, in 2–14 m, over boulders, weed and patches of sand and seagrass. The list of residents is long for such an ordinary-looking structure: nudibranchs, senator and bluethroat wrasse, scalyfin, bluespotted goatfish, southern rock lobster, moonlighters, conger eels, stingrays and, in the seagrass beds alongside, weedy seadragons, with Australian fur seals from Lawrence Rocks occasionally coming into the harbour and, at night, little penguins on the breakwater rocks. Visit Portland adds fish, eels, sharks and crayfish to the roll call. Cuttlefish, octopus and seahorses turn up in the weed.

It is a beginner's dive by design – sand entry, a wall to follow, modest depth, facilities at the shore end – and Portland SCUBA uses it for training; it is also the port's night dive and the fallback when Lawrence Rocks and Cape Nelson are out. Two things need care. Visibility is poor, typically 2–5 m, because of port sediment and easterly swell, so it is a macro and critter dive rather than a scenic one. And the breakwater is Portland's most popular fishing spot, so monofilament, broken and active, is everywhere on the rocks; a good knife and line cutter are essential, a dive flag is required for the boat traffic, and the rock wall itself is steep and slippery for anyone tempted to scramble down it rather than use the beach. The nearby Lighthouse Reef and the New Zealander wreck at the northern end of Nuns Beach extend the same shore-diving ground.

From the centre of Portland follow Bentinck Street north to Lee Breakwater Road, which runs along the breakwater; park on Lee Breakwater Road north of the breakwater near Nuns Beach or further along the structure itself. Gear up at the car – toilets, showers and changerooms are at the shore end – and walk 50–100 m onto Nuns Beach, entering from the sand at its southern end where it meets the breakwater. Follow the outer wall east toward the pump house and wave marker about halfway along; beyond that point diving is conditional on port operations.

Exit back at Nuns Beach. Portland SCUBA in town supplies air.

The Lee Breakwater is sheltered from westerly through southerly swells by the main breakwater to the south and from most winds by the harbour, so it is diveable on most days; the exception is easterly weather, which puts swell straight onto the outer wall and Nuns Beach and stirs the sand. Visibility is typically only 2–5 m because of sediment from port operations and easterly swell, better after a run of calm westerlies. Any tide; high water gives more depth along the inner section.

Night dives are good and safe because the wall is a fixed reference. Check ship movements – the port is busy with woodchip, grain and aluminium traffic.

Enter from the southern end of Nuns Beach, descend beside the rocks in 2–3 m and follow the base of the outer wall east, keeping it on your right, through the weed and boulders to 8–12 m near the pump house. Turn at half gas or at the wave marker, return along the wall at a shallower depth over the seagrass looking for seadragons, and exit at the beach. Carry a knife and line cutter.

Portland SCUBA – training dives and guided shore dives; Portland dive club members; Warrnambool Diving on visits. The breakwater is Portland's standard training, check-out and night dive.