Powerboat crews were warned about their speed and the volume of S Club 7 songs pumping from a stereo minutes before a fatal boat crash.
An inquest opened today into the death of 45-year-old Ian Langan, killed by a speedboat driven by his younger brother.
Ian, of Springfield Road, Brighton, was one of four people on the Seadoo, which was in collision with the Blue Sunset just south of Brighton's Palace Pier.
Mr Langan was part of a group who spent the day drinking and socialising at Brighton Marina on August 4, last year.
The force of the collision threw Mr Langan into the sea. He was killed by the Blue Sunset's propellers.
His left hand was severed and he died "almost instantaneously", according to Home Office pathologist Dr Vesna Djurovic.
The Blue Sunset was being driven by 44-year-old Cliff Langan, who was arrested but later released without charge.
Russell Beech, of College Street, Brighton, told the inquest he had been on duty as harbour assistant at Brighton Marina on the day of the tragedy.
He saw the Seadoo travel through one of the locks closely followed by the Blue Sunset.
Mr Beech said: "I noted the Seadoo came into the lock a bit quicker than boats normally do.
"I spoke to them about the waves it was creating. I hoped perhaps they would keep the speed down. They were going a bit too quickly.
"There was a conversation between the people on the two boats and some gestures. I thought it was about the waves created.
"There was also a conversation about the music they were playing. It was pop music, S Club 7."
He said the Seadoo circled a refuelling pontoon once while waiting for the second boat. He saw no problems with the speed or movement of the two boats as they left the lock.
The inquest is scheduled to last three days and will include evidence from 21 witnesses.
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