Three men out fishing for fun died when their boat was almost "run over" by a fishing vessel whose skipper who was not paying enough attention, a court has heard.
David Marr was "entirely distracted" and only found out about the deadly near-miss his scallop dredger had been involved in from the radio, hours later.
Romanian nationals Mercea "Mitch" Ilea, 40, Irinel Popovici, 41, and Treaiam Dumitrache, 50, drowned when waves of seawater gushed into their boat off the coast of Shoreham, West Sussex, on the night of August 5-6 2017.
The fourth man on board - Elvis Cojocariu - was found the next morning, suffering from hypothermia, by a fisherman who was checking his nets.
Marr, 53, of Tower Hill in Peterhead, Aberdeenshire, is charged with failing to maintain a proper lookout on the Vertrouwen boat and appeared at Lewes Crown Court for trial on Monday.
Prosecutor David Richards told the court: "The case focuses on events about a mile and a half off of the Sussex coast in the very, very early hours - about 12.24am - on 6th August 2017.
"It resulted - that very near-miss - in James 2 being swamped and sinking.
"There were four men on board and, of the four of them, only Elvis Cojocariu survived.
"It is very clear on the evidence, say the Crown, that Mr Marr was entirely unaware of the James 2."
The James 2, a 16ft (5m) angling boat, had been bought by father-of-three Mr Ilea and named after his young son for his birthday.
He and the three other men ate dinner at Mr Ilea's house in Brighton on August 6 before leaving at about 7.30pm - the last time his wife saw him alive.
They headed to Shoreham Harbour, where James 2 was moored, and sailed out to sea for about half an hour, the court heard.
Having reached an area where the sea was about 131ft (40m) deep, Mr Ilea cut the engine and they began fishing and drinking a little whiskey.
The prosecutor said James 2 lacked some of the necessary lighting, but "that does not explain" why Marr "appears not to have had the slightest awareness" of the boat.
There were life jackets on board but the four men were not wearing them, the court heard.
They spotted Marr's vessel - the Vertrouwen - about half a mile (1km) away but did not initially think there was any need to worry.
But as it got closer and continued to head straight for them, they realised they needed to take action, the prosecutor said.
Mr Richards continued: "It had not changed course since they first saw it.
"It was heading in a straight line, the same speed, as if on autopilot.
"It seemed to them they were about to be run over.
"Mitch tried to avoid the Vertrouwen by putting the James 2 in a hard right turn but it was too late."
The Vertrouwen passed "very close by" the James 2, which was pushed to one side by the force of the water.
Mr Richards said: "Water flooded in to the James 2 and Irinel and Mitch tried to bail it out.
"The Vertrouwen carried on, same direction, same speed, passing the James 2 and moving onwards."
When Mr Cojocariu looked over at the other boat, he had a clear view of its deck and wheelhouse, but could see no-one, the prosecutor said.
When another wave smashed into the James 2, Mr Ilea shouted: "We are sinking. Jump in the water."
Despite their efforts to swim away, three of the men died. Only Mr Cojocariu survived.
Turning to the actions of Marr, prosecutor Mr Richards said he should have "scoured ahead" once he was clear of the breakwater at Shoreham.
"He should have used his eyes, his hearing and his radar as an aid to determine what traffic lay ahead to see if anything lay in the sea in the course in which he was sailing."
Marr also failed to notice the lights and the shouts of those on board the James 2 as the Vertrouwen passed close by.
He was also the only person on night-time lookout, in breach of guidance, the court heard.
Mr Richards said: "By reason of these failings he did not maintain a proper lookout."
The trial continues.