Police have named the missing Brighton Marina yachtsman as Len King, 74, a businessman from Alfriston.
His wife Stephanie said that he was an experienced yachtsman who had been sailing for more than 50 years.
She spoke after coastguard and RNLI lifeboat crews called off their search for Mr King, who runs SAK Equipment, a precision engineering business, in Eastbourne.
Sussex Police said that Mr King’s disappearance from his Sunseeker yacht Stefefree was now being treated as a missing person inquiry.
The boat was found drifting at Brighton Marina last night (Sunday 9 November) with signs that Mr King had recently been aboard.
An extensive search in stormy conditions failed to find Mr King.
Mrs King, 65, said: “Len is an experienced yachtsman and has been sailing since he was at least 20.
“Normally we go together but during the week if it’s calm weather he may go off by himself.
“He went off just before lunch. I was expecting him home for dinner time.
“I phoned him several times but his phone was unable to connect so I thought he was on his way back. I called the person who has a boat next to us and he thought we were away.
“I can’t understand what has happened. He is a very experienced yachtsman. He has all his equipment doubled up and is always careful. That is the way he runs things.”
Inspector Roy Apps said: “It is an anxious time for the family. The search is currently suspended and we are liaising with his family as we investigate the circumstances of his disappearance.
“An experienced seaman, Mr King had left Brighton Marina on his yacht on Sunday afternoon and it is unclear as to what has happened to him.
“A friend reported him missing to the Coastguard at around 9.50pm last night as he had not returned home.
“His Sunseeker boat was then found unmanned near the harbour wall at Brighton Marina.
“An extensive search was carried out by the Shoreham and Newhaven coastguard rescue teams, Shoreham, Newhaven and Brighton lifeboats along with the coastguard helicopter from Lee-on Solent and this has now been suspended until new information comes to light.
“We are at an early stage of our investigation and we are liaising closely with Mr King’s family while we make inquiries.”
The Maritime and Coastguard Agency said that the alarm was raised shortly before 10pm.
Brighton Marina had been told by a friend of the man that he had not returned home as planned.
Mr King’s yacht was found adrift near the Marina’s harbour wall at Brighton.
An initial search was stood down and resumed this morning.
The Shoreham and Newhaven coastguard rescue teams, and Shoreham, Newhaven and Brighton lifeboats all took part in the search along with the coastguard helicopter from Lee-on-Solent.
The Newhaven and Shoreham Coastguard Rescue Teams have been carrying out extensive shoreline searches all the way around Brighton Marina, including the eastern and western arms of the marina.
Brighton and Shoreham inshore lifeboats have searched all the way around the marina, including in and out of every pontoon.
The Shoreham all-weather lifeboat has carried out searches east from Shoreham to Brighton Marina and back to Shoreham, going as far out as two and a half miles offshore.
The Newhaven all-weather lifeboat has conducted similar searches west from Newhaven to Brighton, again going as far out as two and a half miles offshore.
The Coastguard helicopter from Lee-on-Solent conducted a shoreline search from Shoreham to Newhaven and back again, including all around the Marina. They have also undertaken a search out to mid Channel.
Despite extensive searches, nothing has been found. Unless any new information comes to light, the search has been suspended, the coastguard said.