Can human evolve to sea mammals, just like whales?

Some evolutionists argue that human will not evolve anymore because there is no pressure to evolve. Fair enough. I want to give you a scenario to ponder: what if there are families living by the ocean and spend their whole lives swimming underwater because they are pearl divers. They reproduce among themselves only, just like what pakicetus did millions of years ago. Because it’s beneficial for them to live underwater, in how many generations do you think their children / population will be capable of breathing underwater (or making their nostrils drifted to the top of their heads like blowholes), the skin becomes rubber-like (like orca), develop sonar, and legs morph into flippers?