A Kiwi deep sea explorer has revealed his email exchange with the chief executive of OceanGate, warning of the dangers of the company's Titan submersible.
The Titan went missing while exploring the wreck of the Titanic and appears to have suffered a catastrophic failure, killing all five passengers.
Rob McCallum is an expert in deep-water submersible operations and has led expeditions to the Titanic.
Rob McCallum spoke to Ingrid Hipkiss.
