Jose Ernestor da Silva was fatally attacked on Sunday afternoon while bathing in waters off the Piedade beach near Recife, on Brazil's north-east coast.
According to the Daily Mail, the shark attacked just as lifeguards stationed on the beach told the 18-year-old to come closer to the shore.
Lifeguards rushed into the water to save him and drag him onto the sand. He later died in hospital after having suffered two heart attacks on the way.
Da Silva had his left leg amputated and had veins re-attached to his penis in a three-hour operation as doctors tried to save him, but the victim died hours later.
Miguel Arcanjo, director of the hospital where the teen was being treated, said: 'He arrived unconscious, with an extremely serious injury. After the surgery he was taken to the Intensive Care Unit.
'He lost a lot of blood, which was replaced, but he suffered hypovolemic shock and passed away.'
Jose's mother Elisangela dos Anjos, 42, told Brazil's JC Online that he had gone to the beach without her knowing, and she only knew about it after his his brother Ezequiel, who was with him, called her from the beach following the attack.
Speaking from the hospital, she said: 'He would go in secret, because he knew that I thought it was dangerous. I wasn't worried because I thought he was somewhere around the house.
'When I heard about it I went crazy, all the neighbours heard me screaming.'
This article originally appeared on New Idea.