"Maybe," the Doctor agreed. The bait ball spun madly through the water, and a long tentacle shot out of the sediment, snatching up a fish effortlessly from the group. It sank back down instantly.

"Many things about that are not good," the Doctor pointed out, his voice squeaking slightly out of surprise. That was the same tentacle that wrapped around his leg, the same sort that nearly caused his regeneration. Jack was right, though. No way to find out but to go down.

He took a breath and kicked off, swimming towards the hole they went through before. He swam around Jack, trying to make it to the cave mouth first.