JACKSONVILLE, Fla. -

Five Jacksonville firefighters and one St. Johns County firefighter were on vacation in Key Largo on Saturday when a boat near theirs started taking on water.

The men immediately jumped into action, saving six people from the water.

"It's just an instinct, you know," Matt McCormack, a Jacksonville firefighter, said in a phone interview. "We never thought twice about going over there to that boat."

IMAGES: Firefighters pull boaters from water

The firefighters were lobstering about five miles off the coast of Key Largo. They say seas were 4-6 feet and the wind was blowing 20 knots. Half of the firefighters were on board and noticed the boat near them taking on water.

"It just all happened so fast," McCormack said. "Before we knew it, they were bailing water by the cooler-full out of the front of their boat."

They quickly motored over to the other firefighters, who were snorkeling, to let them know what was going on.

"We were like, 'Hey, hurry up and get in the boat. I think these people are about to sink,'" McCormack said. "And no sooner that we got the last person on the boat their boat is going underwater."

The 23-foot Regal was standing straight up under the water, with only the tip of the bow bouncing above the waves.

"It was so rough out there," McCormack said. "It was very difficult to keep the boat still for them. It was pretty dangerous with that motor bouncing up and down out of the water."

The six people from Fort Lauderdale were floating on cushions and life jackets until the firefighters could pull everyone to safety.

"There weren't any other boats around and they didn't have a radio, so if they'd have gone down without us there, they would've been floating for a little while."

Firefighters had called mayday from their radio, and the Coast Guard and Tow Boat U.S. responded and took over.

It was a job well done for the firefighters, even on their day off.

"You would think as a good-hearted and good-minded human being, if you could help somebody you would, whether you're getting paid to do it or not," McCormack said.

Back on shore, the groups reunited. The South Florida folks were thankful to their heroes from up the coast.

"We were happy to be there for them," McCormack said. "They tried to offer us some money and this and that, and we told them absolutely not, you know. We were really and honestly happy we could help them."