Flood waters this morning (February 1) were filling the pedestrian subway joining the southern and northern platforms of Worthing Railway Station.
Early today, Southern Rail said eastbound trains aren't stopping until at least 10am.
Passengers needing to leave at Worthing's main station were being advised to continue to East Worthing, then change to a westbound train in order to return.
The rail operator said engineers were expected on-site by 8am.
Pedestrians using the underpass can normally hear the waters of the Teville Stream flowing underneath the walkway.
As a result of developments, the old watercourse through Worthing is now culverted for most of its length.
After the railway station, the stream continues into fields near East Worthing railway station — then it meets the Broadwater Brook.
According to Steyning Museum, in February 1832, a 31-year-old smuggler named William Cowerson was shot by a Customs coastguard at a gate at the then Teville Stream Bridge, a mile or so inland from the sea, on the way north to Broadwater.
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