A teenage girl was rescued from the water near Splash Point in Worthing.
Police, an ambulance and the coastguard were called to the incident, which happened at about 7pm last night.
The lifeboat was stood down on route after the girl, who was reported to be in distress, managed to get ashore, a spokesman for Shoreham RNLI Lifeboat Station said.
Sussex Police has thanked everyone involved for their assistance.
A spokesman said: “At 7pm on Tuesday (August 7), police received a report of a young woman in the sea off Marine Parade, Worthing.
“She was assisted by a boat crew who brought her safely back to shore, and was returned home by officers.
“Police would like to thank everyone involved for their assistance.”