Search teams are desperate to find the person after they were seen going into the water earlier.
Only their boat and paddle have returned to shore washing up at Hove Lagoon near Brighton, UK.
Sussex Police, a coastguard helicopter crew and volunteers from the RNLI have joined the search.
A spokesman for HM Coastguard said: “At 10.10am today, HM Coastguard received a report of a person seen going into the water from a kayak or canoe off Hove Lagoon near Brighton.
“Coastguard Rescue Teams from Newhaven and Shoreham joined the search as well as the Brighton RNLI lifeboat and a Coastguard rescue helicopter.
“A kayak and paddle were found ashore in the area.
“The search is ongoing but if you have any information about this, or can confirm if this person has made it safely to shore, please contact the Coastguard as soon as possible on 02392552100.”
Officials have said the hot weather has brought more people to the coastal areas which has caused emergency measures to be at their highest in four years.
On Friday, the Coastguard dealt with more than 329 incidents across the UK and there were 22 helicopter call outs.
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