The most important reason that lakes and oceans have different types of animals life is that oceans have

Oceans are made to support animals that live in salt water. The animals that live in salt water have a special ability to handle the extreme levels of salt. If you have ever went swimming in the ocean and accidentally swallowed some of the water, you may have wanted to immediately throw up or maybe you did. The reason for that is because our bodies do not have the type of build that salt water animals or marine life have.

Oceans have salt water. Most lakes are fresh water.