Watch: Passers-by jump into lake to save pensioner and dog from sinking car

This is the dramatic moment a man and his dog had to be rescued by three brave passers-by when his car plunged into a lake and began to sink.

Footage of the scene shows the trio of rescuers urgently trying to get the man, who was in his 70s, out of the car.

The swimmers - one woman and two men -can be seen banging on the glass window of the car in a bid to break it after attempts to open the door failed.

Fortunately, as the car begins to sink, the lifesavers manage to get the back door of the car open and pull out the pensioner in time.

The SUV started to descend down into the depths. Photo / Alex Kerr / SWNS.com

The incident, which occurred on Sunday afternoon in Welwyn Garden City, Hertfordshire, was filmed by onlooker Alex Kerr, 29, who witnessed the rescue from a nearby cafe after popping out to get a coffee with her family.

The accountant, from St Albans, said: "It was quite surprising to see as we were just sitting and having a coffee when we heard this big crunch noise.

"When we looked up we just saw this car floating into the lake, but it had already gone through a metal bollard and chain.

"It just floated off but it took a while for any of us to realise someone was in there as he was sitting so still inside."

As soon as they realised they jumped straight in to help him, they were great.

"They couldn't get the door open so they tried to break the windows as it was going down and then they managed to open the back door.

"As soon as that door open it started to go down quickly but they managed to get him out and all that ended up showing of the car was the open boot."

Hertfordshire police were called at 12.49pm to reports of a car entering the lake at Stanborough Park.

The rescued man, from Potters Bar, Hertforshire, was treated at the scene and taken to hospital but he is believed to be uninjured.