Littlehampton lifeboat crews did a sweep of the River Arun after reports of red flares going off.
The RNLI and local coastguard rescue Team were tasked to investigate the incident following a 999-emergency call on Tuesday, November 13.
Littlehampton’s D Class lifeboat Ray of Hope and volunteer crew launched at 5.40pm following a call from the UK Coastguard and began a shoreline search along the river.
The harbour master spoke with members of the public who reported seeing similar flares at Littlehampton and Arun Yacht Clubs, according to an RNLI spokesman.
Having completed the shoreline search, the lifeboat was directed to the entrance of the harbour and continued searching around West Beach and east and west of the harbour entrance.
After a detailed search which proved to be inconclusive, the lifeboat was stood down and returned to the station at 6.55pm.