The swimming animation really needs some tweaking. For example:
When sprinting and falling by accident in one deep water, you go into the swimming animation. This makes places like shown in the screenshot a nightmare to travel in. Besides, in real life, you would hurt yourself when you dive in undeep water like this.
While sprinting in water, it's extremely tricky to get above water for air. The animation makes it look like you are barely unable to make it out of the water.
While sprinting in the water, it takes a bit too long to get up one block. You have to "glide up" it before you can attempt to get over one block, or stop sprinting.
The first bullet duplicates MC-125698. Cannot confirm the other two. Also, 1 bug per ticket.