Authorities believe they have “exhausted all opportunities” to find a swimmer believed to have vanished about 100m off a popular beach, with the search to be scaled back.

The man was reported “in distress” off Perth’s Trigg Beach about 5.15pm on Tuesday, before he was “lost from sight”.

Emergency services — including Water Police, Police Air Wing, Volunteer Marine Rescue WA, and Surf Life Saving WA — have carried out land and sea searches along the 20km stretch of coastline between Swanbourne and Sorrento in the time since.

Police divers were also called in on Thursday, yet there has been no sign of the mystery person they could be looking for.

“The male person has not been identified, nor have we been able to locate a swimmer at sea,” inspector Julie Foley told reporters on Thursday.

“Extensive searches have been conducted of surrounding car parks and also the beaches.

“At this time, no items of interest have been located, nor have there been any vehicles that have been located abandoned.”

The swimmer is believed to be in his 20s or 30s and have brown hair, with that description given by another person in the water on Tuesday.

Conditions at the time have been described as “fine”, and “reasonable” on Wednesday, although a turn on Thursday has not helped visibility in the water for police divers.

Also leaving emergency services at a road-block — no one has come forward to report a missing person.

Police are open to possibility the man is a solo traveller.

“At this stage we believe we’ve exhausted all of our opportunities with regards to land and sea searching,” Foley said.

“We do intend to seek information from the public that may give us further advice … but at this stage it will be scaled back.”

Police want to hear from anyone who “perhaps found yourself in distress” but managed to make it back to shore on Tuesday.

Witnesses or people who have have not heard from friends or family members known to have visited Trigg on Tuesday should contact police on 131 444.