A web designer accused of killing a young woman when his speedboat capsized on the Thames admitted: "I did not even ask if she could swim," a court heard.
Jack Shepherd had allegedly tried to seduce 23-year-old Charlotte Brown with a boozy meal at the Shard and a champagne boat trip to Westminster after they met through a dating website.
But after he gave her the wheel for a "thrill", the speeding vessel hit a submerged tree trunk and capsized on the evening of December 8 2015, the Old Bailey heard.
Afterwards, the 30-year-old told police his boat had been going "full throttle".
He said: "Neither of us were wearing life jackets, although there were two between the seats.
"She would not have known they were there and I did not point them out. I did not even ask if she could swim."
Jurors were told that if Ms Brown had been wearing a life jacket, it would have "increased the probability" of her survival in the water.
A post-mortem examination gave the cause of death as cold water immersion.
Prosecutor Aftab Jafferjee QC said Shepherd had been advised by police about wearing jackets on more than one occasion in the past.
On August 22 2015, he had taken a girlfriend to the Shard by boat but she felt "uncomfortable" and left him at the restaurant to take a taxi home, the court heard.
Mr Jafferjee said: "Once again he was speeding, and she will tell you that she became uncomfortable and asked him to slow down.
"Marine police officers also stopped and spoke to him on this occasion. They noticed he was driving, as the officer says, 'at speed'.
"The officer pointed out to him both of them should be wearing life jackets as it was an important safety issue."
Then on September 10, marine police caught up with Shepherd heading upstream towards his houseboat in Hammersmith, estimating he was doing 30 knots, which is more than twice the 12 knot limit.
They advised Shepherd that wearing life jackets was a "sensible thing to do" as well as making sure the kill cord was attached, jurors heard.
Mr Jafferjee said none of the warnings were heeded by the defendant.
On the night of the accident, the boat was estimated to be going on average 30 knots on the way to Westminster and between 22 and 29 knots on the return journey when tragedy struck.
At the time of a "glancing blow" to a large tree trunk, the boat was going about 20 knots, it was claimed, and Ms Brown was in no condition to avert the danger.
The court also heard how the speedboat had a number of defects, including "poor and sloppy steering" and a "partially opaque" windscreen.
Shepherd, who is being tried in his absence at the Old Bailey, denies manslaughter by gross negligence.