Police investigating the death of Leslie Gelberger, who might have been struck by a boat, are looking for two fishermen seen on a dinghy that morning.
The body of Mr Gelberger, a Westlake High School teacher, was found in Auckland Harbour near Mairangi Bay on 21 April.
Detective Inspector Aaron Pascoe said he was thought to have swum out from Narrow Neck Beach just after 10am.
He said police believed Mr Gelberger was struck by a vessel as he approached North Head.
Mr Pascoe said the dinghy was not believed to be the boat which collided with Mr Gelberger but that police need to speak further with the two men about what they saw.