Calvin Kuo, 58, and Phil McCloud, 68, were rescued, the Coast Guard said.
Kuo was found clinging to the hull of a 16-foot skiff capsized near John Sawyer Bank when he was rescued by a good Samaritan, who had called the Coast Guard shortly before noon. A helicopter located McCloud about two miles from the capsized vessel.
They floated in the water for 22 hours, but Phil McCloud's son said Tuesday that his father was certain in his salvation.
"He just knew that he could live, that he would find his way to shore and just kept swimming," said TJ McCloud, who spoke to his father by telephone on Monday from a hospital bed in Miami.
TJ McCloud said the pair were fishing until about 5:30 p.m. or 6 p.m. when they positioned the boat wrong and waves started hitting.
"He said by the third wave there was about 300 gallons of water inside," TJ McCloud said. "Once that happened, the boat filled up with water then capsized from there they knew they were in trouble."
McCloud, whose family calls him a "crazy man of the water," and Kuo were fishing for yellowfin tuna.
"Carolina skiffs float, and so basically he went underneath trying to find the other life preserver and some other supplies like flares and things like that," TJ McCloud said. "So basically he let go of the rope because they were spending all night on top of this thing, and once he got into the water, he held onto this rope and let go of the rope and the boat just started drifting too far apart and you just couldn't catch up."
"The survivors said their boat capsized within one minute of taking on water with no time to call for help," said Senior Chief Jeremy Weaver, a Sector Key West command duty officer.
McCloud and his son run McCloud Aquatics, a regional water treatment consultancy. TJ was out treating algae in a suburban lake when he got the call.
"Don't take anything for granted especially when it comes to the water ... I work on the water and if you are not safe, not prepared, you never know what's going to happen," TJ McCloud said.
The Coast Guard recommends all boaters wear a life jacket, get a free vessel safety check, file a float plan, have a registered Emergency Position Indicating Radio Beacon and check the weather before leaving the dock.
National Safe Boating Week is May 19-25.
Click here for boat safety information