A 24-year-old man from Powys has gone on trial accused of causing the deaths of four people in mid-Wales in April last year.
The family, from Pontypridd, died when their car plunged into Llyn Clywedog, near Llanidloes.
The prosecution argues Gordon Dyche took a ‘dangerous gamble’, which caused the deaths of 66-year-old Emyr Griffith, 84-year-old Phyllis Hooper, 14-year-old Liam Govier and 14-year-old Peter Briscome.
Caernarfon Crown Court heard that on April 20 last year the family were on their way back from a day out in Machynlleth in a people carrier driven by 55-year-old Denise Griffith.
The prosecution says Mrs Griffith was driving in an "exemplary manner" alongside the Clywedog reservoir.
The court heard the defendant was late for work and ‘became impatient’ two cars behind.
It is alleged he tried to overtake when Mrs Griffiths was indicating right to pull into a lay-by to take photos, with the prosecution claiming his driving fell far below the standard of a competent and careful driver.
Mrs Griffiths told the court there was a shunt, describing how she could see rocks, then sky, then rocks again as the car turned over several times and spun down the bank.
She said: "I remember thinking, how long did I have to live? I couldn't undo my seatbelt - it felt like ages. I was taking in water.
“Then the Lord came to help me get out of the window and come to the surface.
"I knew the others hadn't got out."
The prosecution says the defendant admitted he was sorry at the scene and described how he had been running late for work.
Mr Dyche, of Llanbrynmair, denies all four counts of causing death by dangerous driving and four alternative counts of causing death by careless driving.
The case continues.