Indominus Rex was walking in the jungle. She was a bit thirsty, she had just been chasing a large herd of Gallimimus, so she decided to go take a drink at a very large lake.
Spinosaurus had been swimming in the lake, eating fish. But he was quite hungry. Desperate for food, he spots the Indominus Rex drinking. He waits for the Indominus to finish drinking, planning on ambushing her the second she turns around.
Indominus noticed the Spinosaurus waiting while she was drinking. She figured out what his plan was and when she finished drinking, she turned around. She had a little plan of her own.
Spinosaurus fell for the trick and leaped out of the water to try to ambush her, but Indominus turns immediatly and bites into the Spinosaurus' shoulder. Spinosaurus uses his claws to get the Indominus off him and flees back to the water.
Indominus gets arrogant and starts to chase after the Spinosaurus, thinking about how easily she's killed everything so far and thinking this will be just as easy. Big mistake on her part. The Spinosaurus uses his faster and just overall better swimming to his advantage. The Spinosaurus attacks and grips the Indominus with his claws. He scratches her and tries to pull her underneath the murky water. The Indominus struggles and Spinosaurus is having trouble pulling her into the water. He starts to bite at her now and the Indominus bites back. The Spinosaurus is wrestling with the Indominus Rex to pull her under the water, where he'll win the fight and have a great meal.
Indominus uses her tail to smack the Spinosaurus and pushes him away with her large claws. She tries to swim away. The Spinosaurus pursues and once again attacks the Indominus. The Indominus is now both wrestling with the Spinosaurus and trying to swim away at the same time.
The Indominus Rex is close to escaping now, but the Spinosaurus finally manages to pull her underneath the water. The Spinosaurus is holding her under the lake with him. He desperately tries to keep her head under the water while biting at her tough, scaly skin. While madly swinging his arms at her, he claws out one of her eyes. The Indominus Rex lashes out in retaliation and then slaps the Spinosaurus away with her tail. She climbs back on to land. The Indominus and Spinosaurus are both injured, but with the Indominus in a much worse condition. However, the fight is now on land, where the Indominus stands a better chance.
Indominus runs into the jungle with Spinosaurus chasing. Indominus isn't as heavy as Spinosaurus, so she can run faster. She outruns the Spinosaurus and then turns a little to the right and camouflages into the jungle. She waits for the Spinosaurus to run towards her location, she stops camouflaging, and pounces on the Spinosaurus. She bites into his neck and stands on top of his stomach. The Spinosaurus tries to escape, but can't leave and is killed by the Indominus Rex.