The Transportation Safety Board says modifications made to a commercial sports fishing vessel led to a fatal accident near Tofino, B.C.
The 10-metre-long catamaran left Tofino on April 30, 2017, at about 9:30 a.m. with one operator and four passengers for a day of fishing.
The safety board says that during the next few hours as it anchored at different fishing spots, the Catatonic was observed to take on water.
The board says the bilge pumps, navigation and communications equipment stopped working when the operator was unable to start the engines before the vessel tipped.
According to the report, holes drilled into the boat allowed water to drain into the catamaran's pontoons and buoyancy compartments in the stern.
It says the holes had been drilled to put clamshell deflectors over the outlets on the outer side of the hull, to run electrical cables through the stern buoyancy compartment and to allow the fish boxes to be removed from the vessel.
The power arrangement on the boat had also been modified which meant its two batteries drained at the same time, leaving the vessel without a backup power source for the engines, bilge pumps and VHF radio.
Mohan Raman managed the TSB investigation and says the size of the boat means it was exempted from inspection by Transport Canada.
He wants boat owners to make sure they use qualified people when modifying their vessels.
"I hope people read this report and then they take actions and try and fix things using authorized personnel or authorized technicians," he said.
In addition to the modifications to the vessel, the TSB says the emergency position radio indicator beacon was the wrong type and defective. The vessel operator also did not know how to activate the personal locator beacon.
It took an hour and 40 minutes for rescuers to reach the Catatonic, which was eventually spotted by a float plane pilot.
A search-and-rescue team recovered all five people from the water, but two passengers were pronounced dead in hospital.
Two Alberta men, Alvin Beckley and Mike Cutler, were killed in the accident.
With files from Canadian Press