Another teenager was also hit, but authorities said her injuries were less serious.
Witnesses said that Scott Wilcox, 41, Chelsea Gill, 16, and Zac Latawiec, 14, remained out in the open on the beach when the intense storm struck Tuesday afternoon while other beach-goers took cover. All three are from nearby Lehigh Acres.
The storm was so severe that emergency workers who responded to the strike were told to stay in their vehicles until the worst of it had passed.
Wilcox was killed by the lightning. Latawiec was placed in an induced coma, a family friend told WZVN-TV.
Gill was burned but was reported to be talking when paramedics arrived.
"The blood was rolling, just floating down to the water's edge and the water was turning red right there. It was really terrible," said Robert Gustafson, who saw the strike.
Swim Week Miami Beach 2014 [PHOTOS]