Irwin Inlet is a coastal estuary located in the Shire of Denmark, Western Australia. It discharges into the Southern Ocean at Peaceful Bay, where its swift flow carves through sandbars, splitting the beach in two. This ocean entrance creates a dynamic environment with a surf zone, and paddlers should be aware of the strong tidal currents where the inlet meets the sea. The inlet is accessible for launching from several points. There is a boat ramp at Conspicuous Cliff, and private jetties are available for guests at rental properties like the Peacehaven Chalet and Shack in the Bow Bridge area, which also provide canoes or SUP boards for exploring. The Bibbulmun Track hiking trail crosses the inlet via a dedicated canoe service; a boatshed on the western bank contains three canoes for a 150-meter crossing to the eastern shore, a system maintained for walkers that indicates calm water conditions are possible in that upper section.

The overall character is one of scenic tranquility, with views over the water to forested shores. The area is known for abundant birdlife. The inlet is flanked by coastal heathlands and grasslands in some areas. Given its connection to the Southern Ocean, paddlers must plan for wind exposure and fetch, particularly on the lower inlet approaching Peaceful Bay. Tidal currents are a significant factor, especially near the mouth where the flow is swift. There is some boat traffic, as indicated by the presence of a boat ramp. The best conditions for paddling are likely during calmer weather, avoiding periods of strong onshore winds which can create challenging waves at the entrance and choppy conditions within the inlet. The water is saltwater, and the surrounding landscape includes the Walpole Wilderness Area with its tall forests.