Nudists Pete Sferra and Lloyd Fishback were taking a clothes-free stroll through the Castro neighbourhood of San Francisco when they spotted the person they described as a “crazy kind of pirate guy”.

“My buddy Lloyd is a quiet, respectful guy – but he didn’t waste any time and nailed the guy with a right hook,” Mr Sferra told The San Francisco Standard.

Mr Fishback then jumped into the fray by smacking the alleged attacker in the face, after which he apparently left.

The suspect was later arrested and charged with assault with a deadly weapon, San Francisco Police Department said.