Alan Watkins, 50, and his son Arun Leon Watkins, two, were reported missing off the coast at Littlehampton on Sunday night.

They had gone sailing in a dinghy.

Arun’s body was found in the sea on Sunday evening and he died later in hospital.

A Sussex Police spokeswoman said on Tuesday: “We have got an unconfirmed sighting of a body by a member of the public.”

Mr Watkins was reported missing by his wife from their south-east London home on Sunday evening.

An RNLI team searches the river in Littlehampton, West Sussex

He and his son had gone on a pre-arranged trip to Littlehampton.

Their empty 5ft-long dinghy, containing nappies, a child’s armbands, clothes and refreshments, was reported to the Coastguard by a passing yacht at 6.40pm on Sunday.

Ten minutes later the Coastguard received reports saying they had pulled a young boy from the water. He was wearing a sunblock suit but no buoyancy aid.

He received first aid but died later in Worthing Hospital.