Sussex photographer Eddie Mitchell was at the scene – where RNLI and Coastguard teams were being supported by police officers and paramedics.
Photos show a Coastguard helicopter was assisting the search out at sea.
Reports on social media said between 30 and 40 police officers joined the emergency response.
HM Coastguard has since confirmed it coordinated the response to a report of ‘concern for a man in the water’ at Selsey at about 12.50pm on Sunday, December 1.
A spokesperson added: “The HM Coastguard search and rescue helicopter from Lee-on-Solent was sent as well as Coastguard Rescue Teams from Littlehampton and Selsey, and the RNLI's all-weather lifeboat from Selsey.
“After a thorough search, the man was seen to leave the area and no one was found to be in distress. Sussex Police was also alerted.”
1. Selsey search and rescue operation
Dozens of emergency service personnel joined a large-scale search and rescue operation off the coast in Selsey. Photo: Eddie Mitchell
2. Selsey search and rescue operation
Dozens of emergency service personnel joined a large-scale search and rescue operation off the coast in Selsey. Photo: Eddie Mitchell
3. Selsey search and rescue operation
Dozens of emergency service personnel have joined a large-scale search and rescue operation off the coast in Selsey. Photo: Eddie Mitchell
4. Selsey search and rescue operation
Dozens of emergency service personnel have joined a large-scale search and rescue operation off the coast in Selsey. Photo: Eddie Mitchell