Sharks do sometimes prey on whales, but adult whales are massive beasts that can and will kill sharks if they come too close. Calves are sometimes attacked, lone mothers with a calf are preyed upon, but whales often live in pods that defend one another. Even peaceful filter-feeder whales still pack a punch with their tails, whales are social and will defend one another and their sonar (okay, okay, echolocation) gives them immense advantage over sharks.
Fish are deaf or nearly deaf. The shark doesn’t even know the whale has a lock on it and is coming down, hard. The shark will smell the whale but by the time it can see the whale coming it will be too late. The whale can accurately locate the shark from kilometers away and act accordingly.
Credit : Quora
Picture Credit : Google