“I think it’s extremely unlikely anything like that could still exist in here… and I’m not sure campfire horror stories are what’s needed right now. We’re scientists, remember?” Cate’s jaw set. “Most of the ancient life forms we’ve seen to date are relatively small – even the Placoderm. I think a few people just need to stiffen their spine.”

“What about the ghost Dmitry saw on the sonar?” Greg pointed at the Russian engineer. “He thought it was huge.”

Dmitry grinned and hiked his shoulders.

“Siphonophore colonies – jellyfish,” Mironov said, then uncrossed his legs, and smiled at Jack.

Jack stared back for a moment, but then scoffed, and shook his head. Dmitry bobbed his head. “Oh yes, I have heard of this happening. Is possible.”

“What? What does that even mean?” Greg’s head turned from Dmitry to Jack. “That the ghost you saw was a jellyfish?”

“No.” Jack sighed. “But there is a phenomenon that was detected during World War Two, whereby false ocean bottoms, walls, and even large objects were detected by sonar. They were false readings that turned out to be masses of…” he held out a hand.

“Jellyfish.” Cate answered. “And we’ve seen some big bastards down here already, haven’t we Jack?” Checkmate.

“I don’t believe that’s what it was.” Mironov’s lips just quirked up a fraction. “Our object was under significant locomotion.”

Cate’s mouth hung open; what the hell is his game? Mironov pursed his lips and went back to looking at his several screens.

Cate exhaled, and turned to the group. “Look, I know as much as you guys, but there could be a hundred explanations for the sonar shadow. Might have been a jellyfish wall, or for all we know, there could be more modern creatures in here. My gut feel is this enclosed body of water has had periods of open and closure to the outside world. Maybe when the subsurface plates slide and rip apart, and then re-zip – things might have gotten in and out then.” She turned to Abby. “Abby; you’re our geologist, when was the last major crustal disturbance along this coast line?”

Abby looked to the roof, as if searching her memory. “That would be during the Miocene Epoch, around the Langhian Stage – fifteen million years ago, give or take. Significant geological changes right across the North American continent. That was a big one – it was even thought responsible for the Yellowstone hot spots.”

“There you go.” Cate slapped her thigh. “My guess is it might be some sort of primitive whale.” Her eyes slid to Jack, who simply stared in return. Yeah, I’m lying, so what? Her glare said to him.