A dive company had been officially warned over a near-fatal incident just weeks before another dive in which two people died, an inquest has been told.
Tyron North and Daniel Stoneham, both qualified divers, died during a 39-metre dive in Auckland's Lake Pupuke in July last year.
The owner of Helix Training, which conducted the dives, says the instructor on the day was not carrying a knife or torches despite being required to do so.
Haydon Allan told the inquest in Auckland on Monday he conducted an internal investigation, which found that the divers descended too fast into black water.
Mr Allan said they did not carry out the correct procedure when they lost contact with their dive buddies.
He admitted that Helix Training had been issued warnings for failing to notify the Department of Labour about an incident in which Mr Stoneham almost lost his life just a month before his fatal dive.
Dive leader Tangata Vaikai told the inquest he informed the group that it would be a "blackout dive" and to use the safety rope as a guide in their descent.
He said the group "dropped like rocks" and when he hit the bottom of the lake he felt the effects of nitros narcosis and started to hyperventilate, not knowing how to get to the surface. Mr Vaikai said he believed that the men who died got into the same situation.
Earlier, dive instructor Teauriki Tuaana broke down in tears as described how the group failed to follow his instructions by descending in the lake too fast.
Mr Tuaana said the group was meant to drop to 39 metres, but got into trouble minutes into the dive and he lost sight of them. He said he went to grab Mr North, who pulled him deeper into the lake.
Mr Tuaana admitted that he did not have a knife or a torch with him. He said he later heard a rumour that the divers were competing to get to the bottom of Lake Pupuke first.
The inquest before Coroner Gordon Matenga is expected to last two days.
