Water police say a 76-year-old man missing in off Busselton was a keen and experienced sailor, and there is no evidence to suggest he was not wearing a life vest.
Five aircraft and nine boats have been called in to search for the man after his yacht was found in gear and running yesterday.
Insp. Blair said the man had been due to return at 4pm but the yacht was discovered by local marine rescue volunteers about 7km north of the marina with nobody on board about 8pm.
A Water Police spokesman said the boat had been found with only four of the six lifejackets on board, leading police to believe the missing yachtsman may be wearing a lifejacket.
Police were alerted to the fact that the yacht was overdue about 6.30pm, which sparked the sea search.
Sen Sgt Greg Trews said search was focused about 10 nautical miles out from from south of Busselton up to Peppermint Grove Beach, near Capel.
A search was also underway on land.
Sgt Trews said police and marine rescue services had searched throughout the night for the man, buoyed by the knowledge the Australind grandfather was a strong swimmer, and a good sailor.
"He’s very fit and a strong swimmer," he said.
"It was his habit to sail to the Busselton Jetty and back."
Forensic police scoured the boat this morning in a bid to discover clues as to why the man had disappeared from his boat.
Busselton police are standing guard over the boat at Port Geographe as the search continues.
It’s estimated there are now about 40 people, including police and marine rescue volunteers, desperately searching for the man.
Conditions had been relatively calm yesterday afternoon when the man is understood to have disappeared.
The search and rescue effort is expected to continue until sunset tonight, when a decision will be made whether to continue into the night.