ABOARD THE USS ESSEX, Persian Gulf (AP)

Soon after the top U.S. commander in the Middle East boarded the USS Essex in the Persian Gulf, he could see one Iranian fast boat race across in front of the ship, while another shadowed it from the side.

U.S. Gen. Joseph Votel, head of U.S. Central Command, said he wasn't surprised Iran's Islamic Revolutionary Guard Corps took note of the amphibious assault ship as it patrolled Friday in the southern Gulf. The small boats, which were armed, came within about 300 yards of the Essex, and their radio chatter questioned what a U.S. aircraft from the ship was doing.

In a demonstration for Votel, one of the U.S. Marine Corps' stealthy F-35 fighter jets had made a pass around the Essex, and then hovered in the air above the deck for a bit before making its signature vertical landing.

"I really appreciate you arranging for the Iranians to be here," Votel joked to members of the ship's crew. He later told reporters traveling with him to the ship that the IRGC is trying to watch what the U.S. is doing in the region and collect as much information about that as they can.

"It shouldn't come as a surprise that we have some Iranian interest today around perhaps one of the most significant ships we have in the Arabian gulf right now," Votel said.

It's unlikely that that Iran's Islamic Revolution Guards Corps knew that Votel was on the ship. But they may have seen his two V-22 Osprey helicopters landing as well as the F-35 demonstration by a Marine pilot assigned to the 13th Marine Expeditionary Unit on the ship.

The IRGC boats routinely buzz around U.S. ships in the region, taking photos and collecting information. They previously have also launched drones to fly over and observe American ships, triggering concerns that they could possibly interfere with flight operations.

The high-tech F on the Essex were the first of that new aircraft to conduct combat airstrikes, dropping bombs on Taliban targets in Afghanistan in September.

There are multiple versions of the F-35 for the Air Force, Navy and Marine Corps. The supersonic Marine version, which is meant to replace the AV-8B Harrier, can take off over a short distance and land vertically, like a helicopter.

Navy Capt. Jerry Olin, commodore of Amphibious Squadron One, which includes the Essex and two other ships with her in the Gulf, said the Iranian boats acted safely and professionally. It would have been more dangerous if they drove at the ship, or acted in a more unpredictable manner that risked a collision, he said.

Olin added that the small boats often come in "relatively close" and take photographs of the ships. In return, he said, his crew has used loudspeakers to communicate with the boats, and deter them from becoming a danger.

There are hundreds of the Iranian fast boats operating in the region, he said. In the past, the boats have threatened and harassed ships, including as they are trying to pass through the narrow Strait of Hormuz.