In the snapshot of the 1.13 version 10b, when I swim in water and I go straight up to the surface, I stand up in the water and the swiming animation stops. Fine. Now, if I want to swim and breath at the same time, I have to swim ON the water, with the head slighly above the surface to breath, like a normal person does. But when I do, It's like my character swims in the air, just above the water.