A Pennsylvaia man died on Thursday while diving off of Plantation Key, authorities said.
The 52-year-old man, who was not immediately identified, was in a private boat with two friends diving in the area of Davis Reef.
The man signaled that he wanted to surface, and as the two other people surface they looked back and saw that he had slipped back underwater.
One of the friends went back and pulled him to the back to boat, and he was unresponsive.
A boating passing by stopped to help get him into the boat, and 911 was called.
The friends started CPR on the man, but he was pronounced dead at Mariner's Hospital.
An autopsy will be done to determine his cause of death.
Authorities didn't immediately know if the men were participating in the lobster mini-season.