Tributes have been paid to a British student thought to have drowned off the Maltese island of Comino.
Marcus Hughes-Hallett has not been formally identified, but a Cambridge University statement names him.
University bosses said they were "shocked and saddened to hear the tragic news" about the 20-year-old.
Mr Hughes-Hallett, who was studying maths at Queens' College, is said to have got into trouble while snorkelling in caves during a family holiday.
The Foreign Office said it could not confirm the identity of the victim, but stated it was giving consular assistance to the family.
'Talented and popular'
Local police said attempts to save the swimmer's life had been unsuccessful.
A police spokesman said: "He was assisted by some people who were in the area and brought to shore and given first aid.
"He was taken to Mater Dei hospital by a helicopter from the armed forces, but unfortunately died."
Cambridge University said Mr Hughes-Hallett was a "talented and popular student".
He achieved four A* grades in his A-levels and a distinction in the advanced extension award for maths.
His uncle, Andrew Hughes-Hallett, said: "Marcus was an exceptional young man.
"We cannot put into words what a tragic loss this is. As a family we are totally devastated by his death."