ABOARD THE U.S.S. WHIRLWIND, in the Persian Gulf — In the past six months, this small United States Navy coastal patrol ship has engaged Iranian gunboats three times in international waters here.

Crew members on both sides came up on deck to snap photographs or take video from 300 yards away — souvenirs for the Americans, surveillance for the Iranians, Navy officials say — before the vessels went their own ways without incident.

“They eyeballed us, and we eyeballed them right back, but everything was professional,” said Lt. Cmdr. Jared W. Samuelson, 33, the skipper of the Whirlwind and its 27-member crew. “It was not confrontational.” […]