A Bay of Plenty boatie taking his launch from Tauranga across the Whakatane Bar is lucky to be alive after his boat struck rocks throwing him overboard with no lifejacket.

The 69-year-old man and his 59-year-old companion were navigating from Tauranga to Whakatane after dark on Saturday when they made a navigational error striking rocks near the entrance to the harbour.

A 69-year-old man was thrown from a 33ft launch when the boat struck rocks crossing the Whakatane Bar.

The 33ft launch X-Isle became holed and in the impact the 69-year-old was thrown into the water. Neither him or his companion were wearing lifejackets.

'It would appear that he has taken the wrong course in,” says Whakatane Police senior sergeant Bruce Jenkins.

'There's a whole lot of rocks as you enter the harbour entrance. He hasn't just hit a rock in the entrance, he hit one well before the entrance on totally the wrong course.”

The 59-year-old companion called the Whakatane Coastguard, who notified police and began searching for the missing man.

The 69-year-old man spent more than 20 minutes in the water, before he was found clinging to a rock near the entrance.

'He was treated for mild hypothermia. He was okay,” says Bruce.

'The ambulance came down and checked him out. He got medical attention but he wasn't taken to hospital.”

The boat began taking on water and was run aground on the boat ramp to prevent it sinking.

'It's got a pretty good rip underneath the hull, a good split underneath. It was taking on water pretty fast.”

The boat had come from Tauranga but both the occupants were from Kawerau.

Bruce says the pair have had the boat for some time but keep it in Tauranga.

'I don't think they know the harbour entrance that well, especially at night.”