It was a split-second act that changed Sonny Wells' life.
A remorseful Sonny Wells admits the leap was a "stupid" act
And now, the 20-year-old former soldier faces a bleak future after breaking his neck and becoming paralysed after leaping from a seaside pier into shallow water.
Mr Wells, from Waterlooville, Hants, spoke to the BBC to warn others not to follow him into a wheelchair through a practice known as "tombstoning".
Although remorseful, he says that saying "sorry" will not make up for the
anguish he has put his family through.
Speaking from his hospital bed, he admitted it was a "stupid" act but has vowed not to dwell on his actions.
"Looking back I feel stupid for doing it. But at the end of the day you cannot keep looking back," he said.
"What's done is done and you never are going to be able to go back to that day and take yourself out of the water and put yourself back on the pier."
"No Diving" signs line South Parade Pier in Southsea
The keen footballer could be in a wheelchair for the rest of his life after plunging about 9m (30ft) from South Parade Pier in Southsea into 1m (3ft) of water and hitting the bottom last month.
He had to be dragged from the water unconscious and was airlifted by helicopter to Southampton General Neurological Unit.
There, he has undergone an operation where bone was taken from his hip to stabilise his neck.
His father Robbie Wells said anyone caught tombstoning - leaping from a height into water - should realise it's a "selfish" act.
"If it was going to be any of the boys it was going to be Sonny, he's that type of guy," he said.
"He'd been out with a group of friends. They had a couple of drinks in the pub, it was a Sunday afternoon.
"He ran down the pier, took his shirt off and jumped straight off the side.
Robbie Wells surveys the spot on the pier from where his son leapt
"[He thought] the tide was in, but it was not."
"It's just selfish. It's the impact on people around you, not just the injuries, it's the years to come."
Mr Wells has use of his arms but is paralysed in the lower half of his body. He does not know whether he will ever recover use of all his limbs.
He added: "I cannot say 'sorry' for what I've done, well in a way I can but 'sorry' is just a word.
"For all the misery I've put everyone through, all my family have been brilliant and I just want to say to them to be strong."