“Too bad the Navy didn't have GPS back in 1945,” Delgado lamented.

“Yes, the wartime action reports weren't always entirely accurate, especially where locations are concerned. But the destroyer had not traveled very far from shore when it engaged the sub, so their reported position ought to put us in the ballpark.”

When the Grunion reached the marked position, Delgado eased the throttle into neutral and began keying a search grid into the navigation computer. On the back deck, Dirk and Dahlgren unpacked a Klein Model 3000 side-scan sonar system from a reinforced plastic crate. As Dirk hooked up the cables to the operating system, Dahlgren reeled a yellow cylindrical sonar tow fish out over the stern gunwale and into the water.

“The fish is out,” Dahlgren yelled from the back deck, whereupon Delgado applied a light throttle and the boat edged forward. In a matter of minutes, Dirk had the equipment calibrated, resulting in a continuous stream of contrasting shadowy images sliding across a color monitor. The images were reflections of sound waves emitted from the tow fish which bounced off the seafloor and were recaptured and processed into visual recordings of protrusions or cavities on the sea bottom.

“I have a one-mile-square grid plotted around the Theodore Knight's reported position at the time she rammed the sub,” Delgado said.

“That sounds like a good starting range,” Dirk replied. “We can expand the grid if we need to.”

Delgado proceeded to steer the boat down a white line on the monitor until the end of the grid was reached, then he spun the wheel around and brought the boat down the next line in the opposite direction. Back and forth the Grunion sailed, in narrow two-hundred-meter paths, slowly chewing up the grid while Dirk kept a sharp eye for a long, dark shadow on the sonar monitor that would represent the I-boat lying on the bottom.

An hour went by and the only recognizable image that appeared on the sonar screen was a pair of fifty-five-gallon drums. After two hours, Dahlgren broke out tuna sandwiches from an ice chest and tried to relieve the tedium by telling an assortment of weakly humorous redneck jokes. Finally, after three hours of searching, Dirk's voice suddenly cut through the damp air. “Target! Mark position.” Gradually, the fuzzy image of an elongated object rolled across the screen, joined by two smaller protrusions near one end and a large object lying next to it amidships.

“Lord have mercy!” Dahlgren shouted, studying the image. “Looks like a submarine to me.”

Dirk glanced at a scale measurement at the bottom of the screen. “She's about 350 feet long, just as Perlmutter's records indicate. Leo, let's take another pass to verify the position, then see if you can park us right on top of her.”

“Can do,” Delgado replied with a grin while swinging the Grunion around for another run over the target. The second-pass image showed that the submarine was clearly intact and appeared to be sitting upright on the bottom. As Delgado punched the precise location into the GPS system, Dirk and Dahlgren hauled in the sonar tow fish then unpacked a pair of large dive bags.

“What's our depth here, Leo?” Dahlgren called out as he poked his feet through the leggings of a black neoprene wet suit.

“About 170 feet,” Delgado replied, eyeing a humming fathometer.

“That will only give us twenty minutes of bottom time, with a twenty-five-minute decompression stop on the way up,” Dirk said, recalling the recommended dive duration from the Navy Dive Tables.

“Not a lot of time to cover that big fish,” Dahlgren considered.

“The aircraft armament is what I am most interested in,” Dirk replied. “According to the Navy report, both aircraft were on deck when the destroyer attacked. I'm betting those two sonar images off the bow are the Seiran bombers.”

“Suits me fine if we don't have to get inside that coffin.” Dahlgren shook his head briefly, considering the scene in his head, then proceeded to strap on a well-worn lead weight belt.

When Dirk and Dahlgren were suited up in their dive gear, Delgado brought the Grunion back over the target position and threw out a small buoy tied to two hundred feet of line. The two black-suited divers took a giant step off the rear dive platform and plunged fin first into the ocean.

The cold Pacific water was a shock to Dirk's skin as he dropped beneath the surface and he paused momentarily in the green liquid, waiting for the thin layer of water trapped by the wet suit surface to match the warmth of his body heat.

“Damn, I knew we should have brought the dry suits,” Dahlgren's voice crackled in Dirk's ears. The two men wore full-face AGA Divator MKII dive masks with an integrated wireless communication system, so they could talk to each other while underwater.

“What do you mean, it feels just like the Keys,” Dirk joked, referring to the warm-water islands at the south end of Florida.

“I think you've been eating too much smoked salmon,” Dahlgren retorted.

Dirk purged the air out of his buoyancy compensator and cleared his ears, then flipped over and began kicking toward the bottom following the anchored buoy line. Dahlgren followed, tagging a few feet behind. A slight current pushed them toward the east, so Dirk compensated by angling himself against the flow as he descended, trying to maintain their relative position over the target. As they swam deeper, they passed through a thermocline, feeling the water temperature turn noticeably colder in just an instant. At 110 feet, the green water darkened as the murky water filtered the surface light. At 120 feet, Dirk flipped on a small underwater light strapped to his hood like a coal miner. As they descended a few more feet, the elongated, dark shape of the Japanese submarine suddenly grew out of the depths.

The huge black submarine lay quietly at the bottom, a silent iron mausoleum for the sailors who died on her. She had landed on her keel when she sank and sat proudly upright on the bottom, as if ready to set sail again. As Dirk and Dahlgren drew closer, they were amazed at the sheer size of the vessel. Descending near the bow, they could barely see a quarter of the ship before its bulk disappeared into the murky darkness. Dirk hovered over the bow for a moment, admiring the impressive girth, before examining the catapult ramp that angled down the center deck.

“Dirk, I see one of the planes over here,” Dahlgren said, pointing an arm toward a pile of debris lying off the port bow. “I'll go take a look.”

“The second plane should be farther back, according to the sonar reading. I'll head in that direction,” Dirk replied, swimming along the deck.

Dahlgren quickly darted over to the wreckage, which he could easily see was the remains of a single-engine float plane dusted in a heavy layer of fine silt. The Aichi M6A1 Seiran was a sleek-looking monoplane specially designed as a submarine-launched bomber for the big I-boats. Its rakish design, similar in appearance to a Messerschmitt fighter, was made comical by the attachment of two huge pontoons braced several feet below the wing, which looked like oversized clown shoes extending beyond the fuselage. Dahlgren could see only a split portion of one pontoon, though, as the left float and wing had been heared off by the charging American destroyer. The fuselage and right wing remained intact, propped up at an odd angle by the damaged pontoon. Dahlgren swam to the seafloor in front of the plane, studying the visible undercarriage and wing bottom of the bomber. Moving closer, he fanned an accumulation of silt away from several protrusions, revealing a set of bomb grips. The clasps that secured the bomber's payload were empty of armament.

Gliding slowly up the side of the fuselage, Dahlgren kicked over to the half-crushed cockpit canopy and wiped away a layer of silt from the glass enclosure. Shining his light inside, he felt his heart pound rapidly at the startling sight. A human skull stared up at him from the pilot's seat, the bared teeth seeming to smile at him in a macabre grin. Playing the light about the cockpit, he recognized a pair of deteriorated flying boots on the floorboard, a sizable bone remnant jutting out of one opening. The collapsed bones of the pilot still occupied the plane, Dahlgren realized, the flier having gone down with his ship.