Richard White, 47, was with his son Ashley, 16, in a boat designed for one person when it sank after being hit by a small wave, an inquest in Cardiff was told.

Ashley White: Rescued from water

The teenager had frantically tried to save his father after the six-foot craft sank, pitching them into the cold water.

Former Cardiff harbourmaster Robert Summers said the dinghy carrying the Whites was only meant to hold one person.

Mr White had been warned the boat was very unstable and was unsuitable for use in Cardiff Bay.

The Whites had been heading for the fishing boat Sarah Louise when the tragedy happened, the hearing was told.

I was being pulled away from the jetty by the current and then I couldn't see my father

Ashley White, victim's son

Their dinghy was hit at an angle by a one-foot high wave, which sent water into the craft, lifting it into the air, Ashley said.

"The water was very cold and took my breath away and I was struggling and shouting for help," he told the hearing in Cardiff.

"My dad was five feet away and was struggling as well and splashing in the water and heading for the jetty.

"I went under and when I came back to the surface, all I saw was my father's arm out of the water.

The accident happened in Cardiff Bay

"I grabbed him by the scruff of the neck and his head came out of the water and he was gasping for breath. I was being pulled away from the jetty by the current and then I couldn't see my father."

The teenager then felt himself being grabbed and realised it was not his father, but another rescuer.

A marine diver recovered Mr White's body just 15 minutes after he had disappeared.

Efforts on the dockside to revive him were unsuccessful and he was later pronounced dead at the University Hospital of Wales, Cardiff.

Six men, including building workers and off-duty police officer Jason Hassall, were honoured with awards from the Royal Humane Society for their bravery in the rescue attempt.

Eyewitness: Builder Gary Pullen

A post mortem examination could not find the cause of Mr White's death.

Recording a verdict of accidental death, Cardiff Coroner Dr Lawrence Addicott decided it was likely cold water had caused him to stop breathing and suffer heart failure.

Earlier in the hearing, Pc Hassall said he had been walking along the waterfront when he saw a group of builders running into the water.

He rang 999 and then raced after them, catching up just as they had swam out and pulled the teenager into the shore.

When he was told there was another man still under the water, the Pc dived in to help in the rescue.