How does the open water mixed relay work?

• The team: "Two (2) female and two (2) male competitors from the same country".
• The distance: each competitor completes a lap of 1.5 km.
• The order: competitors "may swim in any sequence, but may only swim once".
• The start: all teams together, in a platform order decided by random draw.
• The zone: a changeover zone at least 5 m long.
• With a platform: "the following competitor may start with a dive from the opposite side of the platform immediately after the arriving competitor touches the platform". Relay platforms are used at all World Aquatics events.
• In the water: without a platform, the next swimmer waits in the water holding the platform, and the touch between the two "should be made above the water anywhere between the elbow and the hand". The contact must be visible.
• Coming and going: a swimmer may enter the zone when their team-mate is approaching and leaves the water at once after their lap.
• Caps: the whole team wears the same caps.
• The judge: a relay judge makes sure each arriving swimmer completes their lap before the next departs.

This is a mixed relay in the glossary's sense: two men and two women.

Letting teams choose their order turns the relay into a tactical race, with men and women swimming against each other on some legs. A visible touch, above the water or on a platform, gives the relay judge something to see in a place where a pool-style touch on a wall is not possible.