A man has had a leg bitten off and the other severed below the knee in a shark attack near Cape Town, South Africa.
Michael Cohen, a 42-year-old thought to be a British citizen, was swimming at Fish Hoek Beach, even though the area had been closed after a shark sighting.
A white flag warning of the presence of a great white shark was flying.
Amateur footage showed Mr Cohen being airlifted by helicopter from the scene and a large shark in the water. He is said to be in a critical condition.
The victim, believed to be a British expatriate living in South Africa, entered the water about an hour-and-a-half after the shark had first been seen.
"It appears [the victim] was rescued from the water by a bystander who left the scene before we could identify him," National Sea Rescue Institute spokesman Craig Lambinon told the South African Press Association.
"The man was conscious when paramedics attended to him on the beach, but was sedated on-scene by paramedics in their efforts to stabilise the patient."
Professor Andrew Nichol, a trauma surgeon in South Africa, operated on Mr Cohen, who he described as "critical but stable, on extremely strong antibiotics and going into theatre again tomorrow".
He also said Mr Cohen had needed seven litres of blood after suffering from massive blood loss, and credited a first aider on the beach who he said had applied a wetsuit as an "amateur" but effective tourniquet.
Prof Nichol also said he had spoken to the victim's family, describing them as "traumatised" by the incident.
A Foreign Office spokeswoman said: "We are aware of reports that a British man has been attacked by a shark off the coast of South Africa. We have offered consular assistance."