The owner of a boat on which two Northumberland fishermen died of carbon monoxide poisoning has pleaded guilty to breaching safety laws.
Mark Arries, 26, and Edward Ide, 21, were found dead on the fishing vessel Eshcol as it was moored in Whitby harbour in January 2014.
The pair were using the grill of a gas cooker to warm the boat overnight as they slept.
A trial of issue is being held at Leeds Crown Court to determine if boat owner Timothy Bowman-Davies was aware that the crew were using the cooker as a heating source.
Bowman-Davies, 44, from Haverford West, Pembrokeshire, admitted failing to ensure that the ship was operated safely and that work equipment was maintained efficiently.
The court heard that Mr Arries, from Blyth, and Mr Ide, from Amble, arrived to work on the boat on January 8 2014.
They were part of a fleet of three vessels fishing for scallops in the North Sea and had returned from a trip in the early hours of the morning of January 15.
The court, which is sitting without a jury, heard that Bowman-Davies's son Jake, who was 15 at the time, was working on one of the other boats and found the bodies of his colleagues.
Giving evidence, he said he boarded the Eschcol after getting no response from its occupants.
He said: "There was like a vapoury smoke, there was no air, that's how it felt. It was warm in there."
He told the court the grill was on and he found Mr Arries and Mr Ide in their bunks, adding: "I tried to wake them up but nothing."
The 19-year-old said each of the three vessels was provided with a fan heater for warmth and could access power from the engine, a generator or an electric hook-up in the harbour.
He said he offered the two men a power cable after they moored in Whitby but they refused.
The court heard that he provided two signed witness statements to police shortly after the incident in which he said he and his father were aware of the cooker being used as a heater on the Eshcol but it was only ever used in "short bursts" of 10 to 15 minutes.
But the witness, who had little formal education and has limited reading and writing skills, said he had not told the police this information and had not read the statements before signing them.
He told the court he had once found the grill on in the Eshcol, when the vessel was being operated by its previous skipper, but did not know what it was being used for.
He said he never saw the cooker being used as a heater and that his father, who did not work on the boats and was only present to transport the fish after unloading, was not aware it was being used that way.
A report by the Marine Accident Investigation Branch (MAIB) found that no carbon monoxide (CO) alarm was fitted on the boat, there was no ventilation, heaters did not work or were damaged, guidance and instructions had not been followed during the installation of the cooker and the management of the vessel was ineffective.
The MAIB said recommendations had been made to the Maritime and Coastguard Agency, which were intended to ensure that the accommodation areas in all small fishing vessels were fitted with a CO alarm.
At an inquest in 2014, a jury returned verdicts of death by misadventure and the coroner also said he would be recommending that boats were fitted with alarms.
The two-day hearing at Leeds Crown Court continues.