Marathon swimming sees athletes take on a 10 km course in open water such as rivers, lakes, the sea and waterways.

The race shall be held in brackish or fresh water bodies with slow currents and low waves, with certification of cleanliness of water quality and personal safety factor in the waters required. The minimum depth of water must be 1.4 metres at any point on the course, and the water temperature should be a minimum of 16°C and a maximum of 31°C. The athlete with the shortest time wins the race.

All open water events are freestyle events.

Open water races feature a closing time according to the distance calculated from the time the first athlete arrives at the finish line. The closing time for the 10 km marathon swimming is 30 minutes after the first athlete arrives.

The marathon swimming of the Hangzhou Asian Games will be held in Chun'an Jieshou Sports Centre Swimming Course from October 6 to October 7, where the athletes will compete for 2 gold medals.