A day at the beach turned into a wild San Francisco brawl after two men began throwing punches in the sand — with one claiming he was simply walking his dog when the confrontation erupted.

The melee unfolded Tuesday at Crissy Field, on the northern shore of the San Francisco Peninsula, and was caught on video.

A reporter for KRON was at the beach for another story and said he heard yelling coming from the water before spotting the two men wrestling and throwing punches in the sand.

One of the men, James Hidalgo, said he was out walking his dog, Argis, when a man he described as loudly talking approached him.

“He said, ‘Are you calling me a dog?’ Because I had a dog, I guess,” Hidalgo told the outlet.

Hidalgo said he tried to defuse the confrontation, telling the man he had no idea what he was talking about — but the situation quickly turned physical.

“And then he came in and he tried to punch me so then I pinned him down to the ground until the cops got here,” Hidalgo said.

The man remained pinned in the sand for several minutes as witnesses called 911.

When United States Park Police officers arrived, both men were handcuffed and questioned.

Hidalgo, a martial arts instructor and former United States Marine, said he understood the need to let police handle the situation.

The martial arts instructor told the outlet he understands there’s “protocols to all this, and you just have to let the professionals deal with what they do.”

Hidalgo was released after being checked out by paramedics, while the other man remained handcuffed and was taken away by police, according to the outlet.

But Hidalgo said he was thankful the confrontation happened with him rather than someone who might not have been able to defend themselves.

“Imagine a nanny with her kid here. What is she going to do?” the martial artists said.

“The guy, he was a built guy, and he knew that he could probably intimidate 90 percent of the people today. He just ran into the wrong person.”

Hidalgo said he plans to press charges.