Eel shark

It was something dark, rising above the surface of the water, pushing out from shore. Then it stopped, roared, and dived, rising with some huge form in its grasp, thrashing and snapping. “An eel shark!” shouted Ishara. “But what is fighting it? Not a dinosaur!”
The struggle was furious but brief. Whatever the dark creature was, it had powerful limbs, and it seemed to break the spine of the predator it fought. It turned and waded from the water, dragging the carcass behind it. After beaching the huge shark-like creature, it “rose, seemed to glower around the bay, and then — drummed its chest.
“A Kong!” Ishara said. “It’s a Kong! They do live!”
“We are not going after it,” Kublai said with determination.


King Kong of Skull Island: Skull Island Journal, Encounters section