The search operation, which has spanned from Barwon Heads across the bay to Point Nepean, is now a recovery effort with police confirming there is little chance Ms Lee could still be alive.

The 42-year-old Preston woman was scuba diving off the Bellarine Peninsula on Saturday when she lost contact with her diving buddy.

Ms Lee's sister has been notified by police but was not at the scene today.

Inspector Gary Bruce said the equipment was found by police divers on the sea floor near the SS Coogee.

“At this stage we haven't confirmed (it belonged to Ms Lee). There are no positive markings on the equipment and we'll be working our way through that,” Insp Bruce said.

“It's extremely unlikely she could survive that amount of time in the water.

“At this stage things are still up in the air because we haven't located the diver.”

SES and police rescuers will widen their search tomorrow, when conditions are expected to worsen.

A team of water police divers have been using tidal mapping to search for Ms Lee.

It is believed Ms Lee's body would not resurface for some time, if she was still wearing her weight belt.

SES and police concentrated their efforts near Barwon Heads for about two hours today after receiving a reported sighting of a figure in the water about 200m off shore.

A member of the public also reported seeing a flipper just before midday.

But both leads have so far been unsuccessful.

Queenscliff Sergeant Steve Brand said the flipper did not appear to belong to Ms Lee.

Ms Lee’s dive buddy, who was resurfacing with her when she went missing, is helping police with their investigation.

Dive Victoria’s Jason Salter said the Ship’s Graveyard area, between Pt Lonsdale and Ocean Grove, was a popular diving site with about 50 wrecks of between 26m and 80m deep.

Most of the wrecks near where Ms Lee was last seen were flat and it would be unlikely a diver could become stuck, Mr Salter said.

“Every diver is trained to be able to firstly prevent trouble, number one, and when everything is followed there’s virtually no reason for anyone to get in trouble but what happens when people get in to trouble is that those things don’t get followed or there’s a medical problem and it’s completely out of their control, or there’s an equipment failure,” he said.

Ms Lee was wearing a weight belt at the time.

But it is as yet unclear whether she was able to remove her weight belt and police divers have not uncovered any of her equipment.

Mr Salter said divers were trained to remove their weight belts if they were in trouble.

“The wetsuit a diver wears, particularly in Victoria because it’s so thick, is extremely buoyant so a diver will have to wear something like eight to ten or twelve kilos worth of lead just to be able to sink and as soon as that weight belt comes off you can not stay down, irrespective of if your (air) tank is full or empty,” he said.

Leading Senior Constable Mark Braun, of the Search and Rescue squad, said tidal mapping showed it was more likely a body would have floated in a north-easterly direction than towards Barwon Heads.

“But I wouldn’t rule out anything. Obviously the wind is going to have a lot to do with it as well, and we can have wind changes so that may affect it,” Sen-Constable Braun said.

Eight police divers are continuing the search for the 42-year-old Preston woman after she failed to surface from a recreational dive at the SS Coogee wreck, off Point Lonsdale, on Saturday.

State Emergency Service (SES) volunteers are expected to continue searching the shoreline as the search moves from a rescue to a recovery operation.

The woman and her male diving buddy were only 8m - or a minute - from rejoining their boat when they lost contact with each other at about 3.30pm.

An extensive air, sea and shore search has failed to find the experienced diver, who has logged 50 dives.

"There are certainly grave concerns," said the head of the police search, Insp Gary Bruce.

Dive Victoria charter operator Jason Salter said the woman had been diving for at least two years and had done the same dive several times before.

"On their ascent they looked at each other and he made it to the surface and she was just below him, but when he looked back she wasn't there any more," Mr Salter said.

"He looked around for her for a minute or two but she wasn't there. He is absolutely shattered and in shock."

Isolated beaches have been combed, and other possible scenarios include that she may have had equipment failure, suffered a medical condition, become disoriented or lost buoyancy.

Mr Salter said the weekend conditions were perfect for diving, with flat seas and clear visibility for kilometres.

- With AAP