No—humans don’t live underwater.
We’re land mammals, which means our bodies are designed to breathe air using lungs, not extract oxygen from water like fish do. If a person stays underwater too long without air, they can’t survive.
That said, humans can spend limited time underwater:
Divers use equipment like scuba tanks to breathe underwater.
Some people train in free diving and can hold their breath for several minutes.
There are even underwater habitats (like research stations) where people can stay for days or weeks—but they still rely on air supplied from tanks or the surface.
So while we can explore and temporarily stay underwater, we can’t naturally live there like fish or whales.