After a while of walking, he came upon a huge open room, with one gigantic whirlpool of raging water in the center of it. It reminded him of the one he'd landed in, only like, tripled in size, and spinning in loops towards the center.
"Pfft. And I thought I'd seen it all," Zack said as he entered the room. He scanned his surroundings. The ceiling had one huge hole leading up to, what Zack thought, was the surface. The room was a giant dome shape, constructed from deep black wet rock. The ceiling was wet too... Wait...
"It's wet? Even up there? So that means... Could the water level seriously been that high at one point?" Zack questioned himself, looking at the whirlpool, and back at the walls.
"This is just one huge drain! And... Without the water supporting the island, this entire place is going to cave in on itself," Zack realized as his eyes widened. He was partly proud of his detective skills, but that wasn't important. He bolted over to the nearest computer screen, showing a 3D model of the tunnels and cave he was in. As suspected, he was in the center of it all. There had been a bunch of other rooting water tunnels, all connected to the big one in the center. The top of the giant hole, near the surface, was labeled Starting Point for Drainage. Towards the center dome, where Zack was, it was labeled, Collapse/Earthquake Point. Finally, Zack looked at the bottom, where the water would stop draining, which was labeled... Destruction.
"Oh god... First time I've hated being right. This entire island is going under the ocean if I don't stop it!" Zack realised, quickly turning to the pool of water. He took a pokeball from his pocket and launched it into the water. A burst of white energy appeared under the waves, and a Sharpedo quickly leaped out of the water.
"Hey bud, could you uh, swim in the opposite direction of that whirlpool for me? I need you to slow this water down as much as possible," Zack asked his pokemon, who happily obliged. As thanks, Zack through him a treat, and turned to another computer screen. After a lot of studying the screen, he figured out that a bunch of extremely powerful fans had been hooked up at an angle in different parts of the tunnel, which was forcing the water down and out of the island. If he could shut it down somehow, the water would probably jet upwards, back to the surface. Which was also his only ticket out. Now the only question was, where could he shut off the fa-. Zack knew.
"Alright, buddy I'm going to be right back, keep up the good work!" Zack called to his sharpedo, starting to run down the tunnel he came.