He didn't find out the reason for the panic until he was already out of bed and almost dressed.
"Before I got my shoes on, the ship struck aground," Henthorne, who was fired by BC Ferries after the crash, testified Wednesday at the trial of one of his former crew members.
"I recognized immediately what it was. There was no mistaking that we were striking ground and continued to hammer along the rock."
The ferry struck Gil Island off British Columbia's northern coast.
Navigating officer Karl Lilgert is on trial for criminal negligence causing the deaths of two passengers, who haven't been seen since the sinking on March 22, 2006.
Henthorne told the court he rushed to the wheelhouse, where alarms were blaring and officers were already taking their positions. He couldn't recall whether Lilgert was still on the bridge by that point.
He checked the radar and saw the ferry was extremely close to land, he said. Outside the windows of the bridge, he saw mostly darkness, except for a single white light he assumed was coming from another boat several miles away.
"The first thing I did after taking those two glances was to pick up the microphone to the PA system," Henthorne told the jury in the B.C. Supreme Court trial.
"I made an announcement for all passengers and crew to proceed directly to the boat and raft stations."
Henthorne did what he could to save the ship, or at least buy some time.
The first step was to close two watertight doors in the engine room, located on the lower deck, which could prevent water from flowing between compartments. He tried several times to contact the engineering crew to confirm they had a way out if those doors were closed and to ensure no one would get crushed by the doors as they slammed shut.
But there was no response. He ordered the doors shut anyway.
Henthorne then dropped the ferry's anchors, he said, because if the ferry was still aground that might keep them from drifting into the open water. As it turned out, the ship was already floating away from the island into the deep waters of Wright Sound. The anchors were useless.
Crew and passengers were on their way to rescue stations, and Henthorne, who said he spent most of his time after the crash outside rather than in the bridge, gave the order to load up the rafts and boats and get them into the water, he testified.
As the evacuation progressed, a crew member informed the captain that a thick steel band that circles the ship known as the rubbing strake, which rubs against the wharf when the ferry is in dock, was under the water.
It was a significant piece of information, Henthorne said, because that steel band was at the same level as the ferry's vehicle deck.
"From that deck up, there is no watertight integrity," Henthorne told the court.
"In the simplest terms, it means we're sinking and there's no saving the ship."
While crew loaded the passengers, Henthorne ran up and down the ship checking for passengers, he said. He looked inside passenger cabins, but found no one.
When all the other passengers and crew were off the ferry, Henthorne stepped into the final life boat and left his sinking ship.
All the while, crew attempted to count the number of people who made it into the life rafts and life boats, reporting their totals back to the captain, but those numbers fluctuated widely.
There were 101 people on board, and the trial has already heard the numbers ranged from 99 to 103 at various points throughout the night.
"Once a mistake had been made once, there was a doubt concerning every count that was made," Henthorne told the court.
In the end, 99 passengers and crew were accounted for. Two passengers, Gerald Foisy and Shirley Rosette, were never seen again and presumed drowned.
The trial has already heard Lilgert was on the bridge with quartermaster Karen Bricker, his former lover, when the ship missed a critical course alteration and sailed toward Gil Island. It was their first time working alone together since their affair ended.
The Crown has accused Lilgert of failing in his duties by missing the turn, which prosecutors have argued demonstrated a disregard for the safety of the passengers and crew.
The defence has argued Lilgert was saddled with poor training and unreliable equipment, which ultimately led to the errors that caused the crash.
Lilgert pleaded not guilty to two counts of criminal negligence causing death.
His trial is expected to last up to six months.
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