The waves off Key Biscayne were strong, so their 1985 Falcon open fishing boat started to take on water faster than the three men could pump it out on Saturday.
Miami-Dade Fire Rescue spokeswoman Erika Benitez said their cell phones were in a plastic jar. After the boat capsized, the jar with the phones floated back to them.
They were holding on to a floating cooler when one of them was able to get his iPhone's virtual assistant Siri to call 911.
"That in and of itself is amazing," Benitez said.
Fire rescue and police marine units were looking for them when a U.S. Coast Guard crew on a helicopter found them and sent a diver into the water. The men were not wearing life jackets.
The diver stayed until a Miami-Dade Police Department's Marine Patrol Unit picked them up and took them to Bill Baggs Cape Florida State Park's No Name Harbor.
Miami-Dade Detective Dan Ferrin identified the men as Diego Perez, 62, Jorge Luis Colon, Jr., 33, and Jorge Luis Colon, 54. Miami-Dade Fire Rescue paramedics determined they didn't require medical attention.
"All agencies involved worked together to ensure these men returned to shore safely," Benitez said.
Local 10 News' Nicole Alvarez contributed to this report.