The Rottnest Channel Swim is about 19.7 km long, from Cottesloe Beach to Rottnest Island across open ocean.

Quick Scoop

  • Official event distance: 19.7 km (12.2 miles).
  • Course: Cottesloe Beach (Perth mainland) to Rottnest Island across the Rottnest Channel.
  • It is considered a marathon open‑water swim and one of Australia’s most iconic long‑distance events.

Why people say “about 20 km”

In most news, blogs and vlogs, swimmers casually describe it as a “20 km swim” because 19.7 km rounds up and conditions, currents and navigation can make the actual swum distance feel slightly longer than the straight-line course.

TL;DR: If you’re asking “how far is the Rottnest swim?” the accepted answer is: roughly 20 km, officially 19.7 km.

Information gathered from public forums or data available on the internet and portrayed here.