At a depth of forty feet, Austin reversed the pump action to stabilize the platform in a hover. Other controls allowed him to detach the metal clamps that held the submersible on the LRT. The sub’s headlights snapped on. With a whirr of its vertical thrusters, the Subvette rose off the platform and hovered above it.

Austin pushed off from the platform and positioned himself in a sitting position above the submersible. He purged air from his buoyancy compensator and slowly dropped into the passenger seat. Zavala had built extra foot room into the cockpit to accommodate swim fins.

Recognizing the impossibility of working floor pedals with fins on his feet, he had placed the thruster controls on the steering wheel.

Zavala pivoted the submersible around to face inland. Twin cones from the submersible’s high-intensity headlights illuminated the scarred face of a rockslide that sloped down to the bottom at a forty-five-degree angle. The collapsed cliff had broken into fragments that ranged in size from rocks no bigger than a head of cabbage to giant boulders that dwarfed the submersible.

“Your Navigator would have to be one tough hombre to come out of this mess in one piece,” Zavala said. “He’d be crushed down to the size of a beer can.”

“The old guy didn’t survive three thousand years by being a wimp,” Austin said.

Zavala’s gargled chuckle came through Austin’s earphones. “Can’t argue with unreasonable and unjustified optimism. What’s a few hundred thousand tons of rock? Where do we begin the search for our hardheaded friend?”

A flat rock, the size and shape of a banquet table, lay several yards out from the base of the slide. “We’ll use that slab as a starting point,” Austin said. “Work to the right, and move up the slide in parallel tracks until we get near the surface. Then we’ll do a reverse search on the left side of the rock. Keep an eye out for columns, a portico, or pediment. Anything that looks man-made.”

Zavala drove the Subvette along the base of the slide. Startled at the submersible’s approach, schools of feeding fish darted into nooks and crannies. At the outer edge of the rockslide, Zavala put the submersible into a graceful climbing reverse turn. He continued the lawn-mowing pattern, moving back and forth across the face of the slide. Occasionally, he stopped at a promising object and pivoted the submersible so that the headlights could come to bear on the target.

The deep-blue water changed to a shimmering green as they neared the surface.