A student diving course came to a tragic end yesterday after two people failed to surface and a third was rushed to hospital.

The body of one of the divers was found in Lake Pupuke, on Auckland's North Shore, while police divers arrived at the scene late last night to help in the search for the missing one.

The search is continuing this morning.

It is believed five students were joined by three instructors on the dive that was part of a course run by Helix Training for Adventure Education in East Tamaki.

Police said it was not clear what happened before emergency services were called just before 2pm.

It is not clear if the victims were students or instructors but the survivors were last night speaking with police officers.

The body of the dead diver, which was found about 3pm, was taken from a pumphouse behind the jetty on a stretcher last night to a waiting hearse.

A group of young men from the dive course came out of the pumphouse and silently watched as the body was taken away.

Later they walked out on to the jetty for about three minutes and appeared to pray, standing close together at the water's edge. They then walked back inside in single file.

A statement from Adventure Education and Helix Training said the teams were shattered by the tragedy.

"At the moment our total focus is on finding our missing diver and we are doing everything we can to assist the police with their investigations."

They promised a thorough investigation "but our immediate priority is to find the missing person".

Detective Senior Sergeant Brett Batty said that when police responded to the call for help they discovered not all the divers were accounted for.

"As a result of that a significant land and sea search was activated."

The Auckland Westpac Rescue Helicopter circled the lake and a police boat scoured the spot where the divers had been. Police divers are expected to begin searching this morning.

The man taken to North Shore Hospital, possibly suffering from hypothermia, was discharged last night.

Malcolm Kidd of the Dive Centre said he knew one group had cancelled their dive because of poor visibility caused by a week of heavy rain. But he did not think the divers would have got into trouble because of the conditions.

He was perplexed that three divers had been involved in the incident. It was rare to have a diving accident but it was rarer to have a problem on a course, he said.

"The issue I don't think really is environmental. I think it has to either be an equipment malfunction which has happened to one diver and two others have tried to save them.

"Or a person's run out of air and the other two have tried to stop them bolting for the surface ...

"Instead of doing a proper out-of-air procedure - going up to your buddy and sharing the spare mouthpiece that everyone has, they've panicked and bolted to the surface and they've tried to stop them."

Those were the scenarios he could think of that would involve three people.

Yesterday's tragedy is not the first on Lake Pupuke. Last December Raphael Alualu, 16, drowned there after jumping from a cliff in Smales Quarry, and in January 2008 Tevaka Papa, 20, drowned. His body was found 50m from shore and 8m below the surface.

In 2004, Sione Moala died after diving off a cliff.

The lake is up to 57m deep and fills a volcanic crater between the suburbs of Milford and Takapuna.