Five members of the Nature Photography Society of New Zealand died in September 2022 when their boat capsized off Kaikōura after being struck by a whale.
A coroner has ruled their deaths were due to petrol fumes inhaled while trapped under the overturned hull, not drowning.
Flaws in the fuel system allowed petrol to leak into the air pocket where the victims were found, all wearing inflatable life jackets that may have hindered escape.
The Transport Accident Investigation Commission also highlighted failures in emergency systems, though the coroner and TAIC agreed a faster response would not have changed the outcome.
No prosecutions followed.
