I know of something bigger than a Blue Whale!!! =O
It's called Praya Dubia. They can be 120-160 ft longam in reality, its many small organisms in a colony, so the Blue Whale is considered the largest singular animal on earth. However, Praya Dubia is larger. They have organisms used specifically for feeding, attacking and defending. They live in tandem-the attackers kill the prey, the feeders distribute it throughout, and the defenders are the insurance against attacks from deep-sea sharks and whales and even other Praya Dubia.
Praya Dubia lives 700-1000m below sea level. The body and blood of the Praya is perfectly designed to withstand the immense pressure. So well-suited, that, if it goes too close to the surface, is will explode due to the pressure being lifted.
The whale shark is the world's biggest fish. 50-60 ft. However, the biggest fish ever, Leedsichthys, was 70-90 ft. Leedsichthys, although massive, had absolutely no defenses. Many small hunters would form attack groups (and not just the same species. Sharks, reptiles, and crocs that lived in the ocean would all form one group) and attack the defenseless giant Leedsichthys together. Such an attack could take hours, but would provide food for weeks.
Baitehway, the RP be frozed AGAIN.