A dad-of-two died on a "Bounce Till I Die" boat party in Amsterdam after his fiancée surprised him with city break, an inquest heard.
Neil Stewart, 30, from Newcastle, had flown out to the Netherlands with fiancée Chelsea Dixon in November 2017 to meet their friends who had just got engaged.
But disaster struck after Mr Stewart drowned in the North Sea Canal, with witness testimony claiming he jumped into the water "as a silly prank".
His body was only found two weeks later, following a major search by Dutch police.
A post mortem found he had taken cocaine and cannabis before he boarded the vessel.
Ms Dixon had bought the tickets to the boat party as a gift for Mr Stewart, and had arranged for them to attend with their friends, ChronicleLive reports.
While on board, Mr Stewart, who worked as a wind farm rigger, got into an altercation on the smoking deck at the back of the boat and was being kept away from other partygoers while security calmed him down, coroner Karen Dilks was told.
Ms Dixon said he had a couple of puffs of a joint and had eaten "space cake" containing cannabis at a coffee bar earlier that day.
They had enjoyed drinks together throughout the day, with Mr Stewart drinking rum and cokes and Jägerbombs.
Post mortem toxicology tests revealed he had taken cocaine during the day, the inquest heard.
Ms Dixon did not see the confrontation in the smoking area but was trying to calm him afterwards.
When she went to get a chair so she could sit with her fiancé, she discovered just seconds later he had vanished.
"I realised Neil was gone," said Ms Dixon.
"I realised he must have been in the water. There's nowhere else he could physically have been.
"There was a lot of shouting and rushing around. I ran to the side of the boat but I couldn't see anyone. Someone said to me 'he's gone.'
"Everything happened so fast."
Asked if she had seen what happened, Ms Dixon said she did not see him jump, adding: "If there was anything else I would wish for in my life, it would be to have an answer to that question."
She also denied that Mr Stewart had ever expressed any intention of harming himself.
"Neil told me that morning it was the happiest time of his life," she said.
"He always said 30 was going to be his year."
Mr Stewart’s friend and colleague Paul Armes was also on the boat, and told the inquest he realised someone was in the water when the vessel stopped.
The offshore supervisor, who has first aid and water rescue qualifications, told the court he was desperate to save his friend after seeing him struggling in the water.
He wept as he told the inquest: "I wanted to get a rubber ring around me and jump in. I could see Neil at this point but the captain wouldn't let me.
"They said they couldn't put the lifeboat out and said they had requested a helicopter but it could take 15 minutes.
"He was in need and no-one else was helping him. I could see him for 10 minutes and then he was gone.
"I just wanted to help him."
In a statement, witness Kirsty Green said she believed he deliberately jumped from the boat into the canal.
She said: “He was stood alone, smoking and the next thing I saw was him in the air, it looked like it was slow motion.
"He had landed on his back and he had his face up in the water.
"I thought it was some sort of silly kind of prank. He was smiling or laughing in the water.
"I then panicked and called security."
She described the events as "horrendous" and said she saw a light in the water, possibly from Mr Stewart's mobile phone.
Fellow reveller Samantha Godkin said she witnessed Mr Stewart came "out of nowhere" and punch her friend Paul Tomlinson in the face.
The sales assistant said: "We were laughing and joking and my partner had gone to get us a drink. Then all of a sudden out of nowhere someone ran over and punched Paul in the jaw. It cracked it was that loud."
She told the court that guests were issued with safety advice before boarding the party boat.
"You were advised about the issues of being careful and to keep yourself safe," she added.
The inquest continues.