Philippine Sea, August 31 -- There are three sure signs that the remotely operated vehicle is functioning and on the bottom searching for Indianapolis:

First is the sound of the ship's bow thrusters — a grinding roar that wipes out all conversation on the main deck and vibrates through the soles of your feet — an unmistakable signal that Sea Eagle is fighting the ocean current to stay dead on target.

Second is a general air of seriousness that grips the ship. In transit or during repairs, you will always find people swapping tall tales in the mess hall, playing poker in the video room or out on the deck complaining about the weather or the state of the vehicle. But once the rover hits the bottom, it's all business; anyone without a job to do hunkers down in front of a video monitor to stare at the hypnotic images of sand, rock and deep-sea debris cabled back from the ocean floor.

The last sign is the ramrod-stiff line of the ROV cable knifing through the waves. While the vehicle roams the deep, at the surface the umbilical cable seems frozen, unaffected even by the endless ocean swells. It's as if the ship were suspended from the ROV and not the other way round.

For the last 24 hours, these signs have revealed the status of the search for USS Indianapolis: ROV at depth, search in progress, no wreckage spotted yet.

"Okay, guys, we're there."

"Roger that. Start searching."

Conversation on the intercom is terse, an occasional command to shift the ship's position 100 meters this way or that, or a request to verify coordinates.

A Prime Target

It takes hours to pin down the exact position of the ROV on the bottom. The detailed submarine topography from the sonar survey is accurate, but there could be as much as a 300-meter offset between the surface coordinates and those on the floor. Once the offset has been determined, we can correct for navigation and ‘’fly"’ the ROV across the bottom directly to each of five top priority targets selected from the sonar search.

Target 1071, focus of the first extended search, eludes sonar and video for hours, but at 1 a.m. a large gray shadow looms into view on the ocean floor. After staying awake much of the night before, none of the veterans are awake to witness the moment. It is just as well. Target 1071 is the right color and shape to be a hunk of a ruined warship, but it's rock, not steel. The prime target is a washout.

The search team continues to scan the area for additional landmarks to confirm that we are in the right position. By 3 in the morning navigation has locked in and confirmed our offset, and the search moves on to the next most promising target.

One down, four to go.