Cloud is absolutely correct that they have to make a move, as guards are beginning to get back into their normal patterns. With all the interference of both time and death energies in the area, it would be hard for Yuna to isolate where Jack is, for now.

If they choose to go after the Box, Jack indicated they would have to stay low, and go through the maintenance corridors that run the length of the bottom of the Valiant. If they choose to go after the Doctor, their path takes them up and towards the front of the ship. There are plenty of stairwells, some open, some more closed off near the corners. Despite the ship being in the hands of a maniacal supervillain, there are still maintenance maps available with the stairwells marked (Safety First, maintaining the Empire takes the efforts of every one of us! That's the British way!)

Footsteps are sounding on the metal walkways, not too close, but there are an awful lot of them.