Early ancestors of whales seemed to have no chance to survive, and yet somehow they did. Many different species adapted to fit their specific environments, allowing them to exist on a global scale.
Another key to whale and dolphins alike is their ability to communicate. Not only does their echolocation help them to locate food and predators, it allows them to converse with each other with their own unique languages.
Sea mammals have one more adaptation that is remarkably similar to how humans live their own lives. They tend to live in family units. Each species has a different system that has allowed them to survive in the harsh ocean.