Corals

The underwater reef was a massive web of rocks that had giant holes and equally giant rocks creating nonuniform criss-cross latices that made it look as though the giant cliff that once stood here had eroded in a weird pattern.

The submarine got closer and closer to the grand design underneath the ocean and showed a natural beauty that not many had seen.

"How is this possible?" Tony couldn't help but ask out loud.

"It is," Ning said. 

"I'm certain something like this does not exist near the surface. If it did, we would have known long ago. What exists there is nothing but giant landmasses with corals growing on them."

"I'm aware," Ning said. "The top is not the same as the bottom. Which is why we can only travel this way and not from the top."

"Still rocks… they shouldn't erode in such a pattern. How does this happen? Are there weird water currents down here that create such a thing?" he asked.