The pair, en route from Santa Barbara to Canada on an annual vacation trip, were saved thanks to a piece of technology they brought aboard their seaplane and the quick-thinking of two rescue pilots.
Lt. Chris Courtney and Lt. Marshall Burtt, both officers with the Coast Guard Air Station in San Francisco, had already completed two rescues Sunday when a distress call came through around 3 p.m. of a plane in trouble south of Big Sur.
When the Coast Guard helicopter piloted by Courtney, the aircraft commander, and Burtt, the co-pilot, arrived on the scene less than an hour later, they found the plane about one mile offshore and northwest of Morro Bay, in San Louis Obispo County.
"When we got on the scene they [the father and son]had their propeller still going, trying to stabilize the aircraft as best they could," Burtt told ABCNews.com. "They had to cut the engine because the swell was at six to eight feet and the propeller was starting to hit the water."
In a scene that Burtt described as "pretty amazing," the son, said to be in his mid-30s, grabbed his father, in his 70s, and pulled him out of the plane's cockpit and onto its pontoon so that they could be rescued.
"We put the rescue swimmer down and did a direct hoist where he grabbed the father from the right pontoon and hoisted him up into the aircraft and then we sent the rescue swimmer back down to get his son," Courtney said. "Just as we grabbed the son, the plane inverted into the water."
After the rescue, the plane became caught in a kelp field in the water and sank, officials said.
Engine malfunction in the pair's single-engine Cessna 185 plane caused the accident, but it was a $300-$1,500 tool the men had brought onboard that saved them.
"The EPIRB is what contributed to them being saved," said Courtney, referring to the emergency personnel locator beacon the father and son used to alert authorities. The device connects to an international satellite system that detects and locates distress calls so rescuers don't have to spend valuable time searching.
In the father and son's case, that meant being saved just in the nick of time, before the Coast Guard helicopter that found them ran out of fuel and before the men fell into the sea.
"These guys were just in pants and button down shirts so they would have been exposed to the cold ocean and hypothermia would have set in in minutes," said Burtt, noting that by the time they got to shore the rescue helicopter had just minutes of fuel left in its reserves. "Everything worked out just well."
The two men, whose identities have not been released, were not injured. Both had their vitals checked by waiting EMTs upon landing and suffered only from shock and a little cold.
"They were very grateful," Burtt said. "Once we landed they shook our hands and thanked us multiples times."
The Associated Press contributed to this report.