Gatwick Express is running a reduced half-hourly service after flooding affected the line between London and the airport.
Travellers faced severe disruption after a water main burst near South Croydon station, flooding tracks. The Gatwick Express was suspended and trains run by Southern and First Capital Connect operated on reduced timetables.
Some rail services have resumed, but passengers from London to Gatwick are advised to allow extra time for their journeys.
South Croydon and Purley Oaks stations will be closed all day and there are timetable changes to many routes between London and the South Coast.