Two weeks after the fall of Baghdad, U.S. Marine Corps Sgt. Andrew Garrett guides an inflatable boat through a cluster of American warships in the Persian Gulf off southern Kuwait. Beside him on a rubber mat lies one of the Iraq war’s most unusual veterans, a 33-year-old male Atlantic bottle-nose dolphin named Kahili.

Garrett, 26, gently turns Kahili so that his tail is pointed overboard; the dolphin wiggles over the gunwales into the green water. The handler snaps a blue plastic lid off a beer-keg-size barrel of fish, holds it up for the dolphin to see and flings it like a Frisbee 50 feet out into the water. Kahili streaks, the disk disappears from the surface and, in seconds, Kahili explodes out of the sea next to the boat, the disk on his nose. Garrett grabs it and tosses a herring into the dolphin’s mouth. "Kahili’s one of our best," he says.

In March, Kahili, along with eight other dolphins that are a part of the U.S. Navy’s Special Clearance Team One, became the first marine mammals to take part in mine-clearing operations in an active combat situation. Together with Navy SEALS, Marine Corps reconnaissance swimmers, explosive ordnance disposal divers and unmanned undersea vehicles, they helped disarm more than 100 antiship mines and underwater booby traps planted in Umm Qasr’s port by Saddam Hussein’s forces.

In fact, the team proved so effective that coalition forces were able to open Umm Qasr to ship traffic, including the British supply ship Sir Galahad loaded with rice and other foodstuffs, only a week after hostilities began. "Without the dolphins, we would probably still be out there trying to clear those waterways," says Garrett’s colleague, Sgt. Scott Young, 29, who is also a dolphin handler.

In the war, Special Clearance Team One began mine-clearing operations by sending several unmanned sonar undersea vehicles to survey the port’s seafloor. During up to 20-hour sweeps, these 80-pound, sonar-equipped drones—called REMUS, for Remote Environmental Monitoring UnitS—identified more than 200 suspicious submerged objects.

That’s where the dolphins came in. Unlike REMUS, a dolphin can differentiate between natural and man-made objects using echolocation, a sensory system that involves transmitting sound waves at objects and reading the "echoes" that come back from them. They can even distinguish a BB pellet from a kernel of corn at 50 feet.

A dolphin performs its sonar magic by generating high-frequency clicking sounds, which pass through the animal’s rounded forehead (known as the melon), a fat-rich organ that serves as an acoustical lens and focuses the sound like a beam. "In the water it’s like a buzzing or clicking sound, which you can feel when they swim up to you," says Garrett. "They’re constantly checking you out." Sound bouncing off objects travels through the cavities of a dolphin’s lower jaw to the inner ear, which transmits the information to the brain by way of the auditory nerve.

Remarkably, dolphins can change the wave form and frequency of the signals they send out, to gather more detailed information. "The animals can make these changes with incredible precision, in real time, just as they are receiving back the initial echoes," says Navy spokesperson Tom LaPuzza. "They’re like the new video recording machines that can record and play back at the same time."

With survey results from REMUS in hand, teams composed of a dolphin, handler, trainer and boat operator motored out in inflatables to evaluate the suspicious objects. When a dolphin discovered a mine, it would swim back to the boat’s bow and nose an attached disk or ball. In most cases, the handler would then send the mammal back down to leave an acoustic transponder, which generated a pinging sound that divers would later use to locate and remove the mine.

The Navy says that the risk to dolphins in such operations is virtually nil because the animals are trained to stay a safe distance away from any mines they find. What’s more, they say, sea mines are designed to explode only when a large metallic surface, such as the hull of a ship, passes nearby.

Still, the practice of using dolphins as mine sweepers has its critics. The Connecticut-based Cetacean Society International condemns the use of marine mammals in a combat zone. "Even wars have rules," society president William Rossiter said in a statement this spring. "It is evil, unethical and immoral to use innocents in war, because they cannot understand the purpose or the danger, their resistance is weak, and it is not their conflict."

"We treat the animals with the utmost respect," says LaPuzza. "We don’t send them out to do anything that’s dangerous for them." The Marine Mammal Commission, an independent federal agency, reported in 1989 that "Navy protocols for maintaining uniform standards of medical care and husbandry are excellent."

The Navy first began working with dolphins in 1960, when researchers at the Naval Ordnance Test Station facility at Pt. Mugu, California, sought to improve torpedo design by studying the animals’ hydrodynamic efficiency. While the Navy learned little it could apply to torpedoes, Navy researchers did take note of the dolphins’ intelligence, trainability and natural sonar. The researchers began to train dolphins to perform simple tasks underwater. In 1965, a Navy-trained Atlantic bottle-nose named Tuffy dove 200 feet to carry tools and messages to crew members in SEALAB II off California’s coast. In 1970, the presence of five Navy dolphins discouraged underwater saboteurs from entering the water and blowing up a U.S. Army pier in Vietnam’s Cam Ranh Bay; in 1987 and 1988, five dolphins patrolled the waters around the USS La Salle off the coast of Bahrain.

Today, the U.S. Navy Marine Mammal Program at the Space and Naval Warfare Systems Center San Diego spends up to $14 million a year to operate, including training its 75 dolphins and 25 sea lions. The Navy says it hasn’t captured wild dolphins since 1999, when it began a captive dolphin breeding program.

None of the sea mammals should expect a speedy discharge. "It’s doubtful anything man-made will ever match the dolphins’ capabilities," says LaPuzza.