Sean Kingston -- Two Heart Surgeries for 'Shocking Pain'

Sean Kingston says doctors had to perform open heart surgery on him after his Memorial Day weekend jet ski crash -- calling the experience a "life or death situation."

Kingston just sat down for an MTV First special and told Sway Calloway ... when he was being released from the hospital, docs discovered a heart condition that required immediate surgery.

Kingston explains, "I had open heart surgery and I had two other surgeries ... it was a life or death situation."

King says he's now back to "100%" -- and compares the former Marine who pulled him out of the water to an angel ... saying, "It was just like an angel in the sky." Kingston says he's emailed his hero and plans to meet up with the guy in the near future.