Police believe a man missing after a boating accident in the Hauraki Gulf last night is unlikely to be found alive.

Another man was found cold but uninjured on Browns Island by police aboard their launch Deodar III Monday morning.

Police believe a wave swamped their five-metre fibreglass boat, which sank about an hour before dark on Sunday night.

The alarm was raised about 8.30am on Monday morning.

The missing man is believed to be in his 40s and was wearing a lifejacket.

Police and rescue personnel searched two gulf islands on Monday and another team started looking in the channels late Monday afternoon.

But there was little hope of finding the missing man alive.

Sergeant Craig Kennedy of the Auckland police maritime unit said both men wore lifejackets, but were unable to contact anyone for help.

“They didn’t have a VHF radio, but by the speed by all accounts of how things happened, they may not have been able to use that in time anyway,” he told Radio New Zealand.

Police and coastguard boats and helicopters from the Police Air Support Unit and Westpac Rescue have been involved in the search.