The Serpentine River is a 111-kilometre river in the South West region of Western Australia, rising below Bowerling Hill in the Darling Scarp at an elevation of 313 metres and flowing westward and then south before discharging into the Peel Inlet near Mandurah. Known as "Waangaamaap Bilya" by the Indigenous Bindjareb (Noongar) people, the river has sustained communities for millennia and flows through Serpentine Dam, Serpentine Falls, and several lakes including Kerulup Pool, Lake Amarillo, and Goegrup Lake before reaching the estuary. The Peel-Harvey Estuary, into which the river drains, is twice the size of Sydney Harbour.

The paddleable lower reaches form part of the Peel-Harvey Estuary Paddle Trails network, with two named routes: the Heron Paddling Trail (half-day) and the Spoonbill Paddling Trail. The Spoonbill Trail runs upstream from Riverside Gardens across Lake Goegrup and through the connecting lakes of Cogrup, Black Lake, Bulbilba Lake, and Road Lake. A popular guided route covers approximately 10 kilometres, putting in at Greenfields and paddling through backwaters, twists, turns, and bends to the river mouth before returning to Riverview Reserve. A longer 20-kilometre paddle has been run from Karnup Road southward, passing through Guanarnup Pool and Yalbanberup Pool, with Lunch Island serving as a midpoint rest stop.

The primary access point is Riverside Gardens Foreshore, which features an all-abilities paddle launch with a large floating platform, contrasting colours, kick plates, grab rails, ramp access, step seating for transitioning from a seated position into a watercraft, and two custom slipways. ACROD parking, accessible toilets, accessible BBQ and picnic facilities, and a car park are all available at this site. Additional boat ramp access exists at Nairn Road, Birchley Road, and Redcliffe Road, with small watercraft launching also available at Redcliffe Road.

Wildlife along the river includes black swans, ospreys, pelicans, yellow-billed spoonbills, and wild dolphins in the estuary. Boating traffic increases during peak season (school holidays), though it is generally less congested than the nearby Murray River. Paddlers should be aware that algal blooms can occur during warmer months, particularly in the upper reaches following hot weather. Navigation can be difficult in some sections, obstructions may be present, and rest sites can be hard to access depending on river levels. Mosquitoes are a consideration, and paddlers are advised to use insect repellent. Western Australia Boating Rules and Regulations apply, and paddlers must keep to the right in boating channels and canals.