Blackwall Reach is the deepest part of the lower Swan River, where the channel runs beneath the limestone cliffs of Blackwall Reach Reserve in Bicton. It is known locally as a cliff-jumping spot and to divers as a river site for days when the ocean is closed. Depths reach about 15 m close to the bank and about 18 m at the barge site.

The bottom is a mix of sand, rubble and a great deal of human debris: dumped cars (the Marine Life Network counts three), a sunken barge whose history is known, and metal scrap. Divingwawrecks also lists three unidentified modern motorboats and cruisers that are hard for shore divers to reach. The debris gives shelter to small fish, and the site has more to it than first appears.

Marine life is sparse but interesting. White-spotted and moon jellyfish are often abundant, cardinalfish (including breeding males carrying eggs in their mouths), gobbleguts, bream, stripeys and toadfish live around the debris and the bank, and seahorses and nudibranchs turn up.

Visibility is usually poor, at 0.5–4 m, and the river is busy with ferries, recreational boats and jet skis. Divers must use a flag, stay near the bank, ascend slowly and wear gloves because of sharp metal.

Blackwall Reach suits experienced divers who are comfortable in low visibility and want a river dive with some depth. It is not for beginners.

River temperatures swing more than the ocean: about 22–26 °C in late summer but as low as 13–15 °C in winter, when a 7 mm suit or drysuit makes a long dive more comfortable. Rinse gear well afterwards, as the estuary water is often high in organic matter.

From Canning Highway turn onto Point Walter Road, then Kent Street, which ends at Blackwall Reach Parade in Bicton. Park and gear up at the car park at the bottom of Kent Street. Walk to the small beach, then continue north-east along the riverbank for about 200 m, walking and wading, before entering.

Mooring buoys 527 and 716 are the usual descent points. About 15 minutes from Fremantle and 20–25 minutes from the Perth CBD.

As a river site it is not affected by ocean swell, which is why divers use it when the coast is closed. Tidal flow is the main factor: currents are stronger towards the middle of the river, so dive around slack water and on neap tides. Visibility is 0.5–4 m and is reduced by Fremantle Port dredging, winter rain (tannin and runoff) and summer algal blooms.

Water is colder than the ocean in winter.

Walk and wade along the bank, then descend at mooring 527 or 716. Explore the dumped cars and metal debris on the slope, staying near the bank, then head for the barge at about 18 m if conditions and training allow. Return up the slope and ascend close to the bank, watching for boats.

Dived independently and by local clubs, mostly when the coast is weathered out. No regular commercial trips.