* Respiratory system: Blue whales are mammals, and like all mammals, they breathe air. However, their lungs are adapted for life underwater and they have a special adaptation called a blowhole on top of their head to breathe. They cannot take in enough oxygen to survive for very long outside of water.
* Weight and buoyancy: Blue whales are incredibly massive, and their bodies are built for buoyancy in water. Out of the water, their immense weight would crush their internal organs.
* Skin and temperature regulation: Their skin is designed for underwater life, and they rely on the water to keep their huge bodies cool. Out of water, they would quickly overheat and dehydrate.
In short, blue whales are entirely reliant on the ocean for their survival.