When I went diving I would wear goggles, the reason as you all know is that without them the water distorts and warps our view.
Some children actually possess the ability to see underwater relatively clearly, as their lenses are more flexible and can adjust to the difference between seeing in air and water. Scientists studied this in Thailand's Moken tribe's children and also found it was still somewhat possible in European children, just with more eye irritation and less clarity.
It's due to the refractive index between the air and your eye vs between water and your eye. When light goes from one medium to another its path gets bent. You can see this when looking into a glass of water with a spoon in it, the spoon doesn't line up. So when you open your eyes in the water, the light gets bent in a way your eyes haven't adapted to deal with and still focus.
I think I read that pearl divers have adapted to be able to focus under water.
But for the rest of us? Our eyes need air directly in front of them to be able to focus properly. The reason has to do with the way that your cornea bends the light as it enters your eye; when touching water, nowhere near as much of this bending is possible.