Police won't lay charges following the death of Auckland swimmer Leslie Gelberger who was believed to have been hit by a boat while out swimming.

Gelberger died on April 20 this year after going for a swim on Auckland's North Shore.

He failed to return from an ocean swim that started at Narrow Neck Beach. His body, missing a leg, was found floating off Mairangi Bay a day later.

Ports of Auckland previously confirmed it was being investigated, after it was thought one of their pilot boats had been involved.

Auckland City police's Detective Aaron Pascoe confirmed today that no criminal charges would be laid.

"Police sought legal advice from the Crown Solicitor who considered the law as it relates to the case," he said.

"Following this police have made the decision that there is insufficient evidence to file any criminal charges."

The matter would be referred to Maritime New Zealand and the Coroner.

No criminal charges would be laid following the death of teacher and ocean swimmer Leslie Gelberger in April. (Photo / NZ Herald)

"Therefore police are unable to make any further comment at this time," Pascoe said.

"We have advised Leslie's family of this outcome and we continue to offer them support as they grieve the loss of a much-loved husband, father and family member."

Ports of Auckland chief executive Tony Gibson said in a statement he understood no charges would be laid, and would "continue to cooperate with authorities on this matter".

"The New Zealand Police have been investigating the possible involvement of a Ports of Auckland pilot boat in the death of Mr Leslie Gelberger in April this year," he said.

"While the police investigation is over, I am conscious that this is still an ongoing tragedy for the family of Mr Gelberger and I would again like to extend our deepest sympathies to them.

"It is not appropriate for us to comment further at this stage."

Gelberger was from Canada and a teacher at Westlake Girls' High School.

Gelberger's family had asked for privacy.

His wife Laura McLeod previously told the Herald the father of two was her best friend.

"I have lost my best friend, the best father to my boys and the most amazing, kindest, positive and adventurous person I have ever known," she said at the time.

"I didn't believe that Hollywood romance was real until I met him. He was the yin to my yang and I really don't know how we are going to cope without him."