Holidaymakers saved a man who became unconscious after "tombstoning" from a rock 20 metres into the sea.
The victim was given first aid on the beach after being rescued
The man, aged 26, climbed up the famous Durdle Door rock in Dorset and egged on by three friends jumped off on Saturday afternoon.
The friends, two men and a woman, fled the scene but a holidaymaker swam out to the unconscious man and got him into an inflatable dinghy.
A doctor on the beach stabilised the man before emergency services arrived.
The man was airlifted to hospital in a coastguard helicopter.
A Portland Coastguard spokesman said: "Seemingly egged-on by two other lads and a female - all of whom ran away from the scene - he jumped off from above the arch, disappeared below the surface and didn't resurface.
"A member of the public saw the jumper unconscious and fitting on the sea bed and surface-dived down and pulled the casualty to the surface.
"Members of the public managed to get the injured man onto an inflatable dinghy and drag it out of the water, keeping him lying down flat, and fortunately there was a doctor on the beach who was able to attend immediately.
He was airlifted into coastguard helicopter and flown to Dorchester
"It is very likely these two members of the public saved this lad's life."
Ros Evans, watch manager at Portland Coastguard said: "This behaviour is plain stupid. Young men are dying pointlessly and getting seriously injured every summer in a bid to impress their friends.
"Rescue services and the families of casualties deal with the consequences.
"This young man jumped from the top of the precarious cliff arch of Durdle Door from a height of at least 20 metres, so an injury was almost inevitable."