Shield mechanism in water bug

Shield cannot be activated in water, unless I hold 'down' button on the rightside of the screen ('shift' key on PC). However, doing so makes the player move bottom of the water which is not as expected.

What is expected: Using shield in water shouldn't sink the player quickly.

Screenshot 1: Missing sneak button to use shield while the player is in water.
Screenshot 2: Holding the 'down' button activates shield but makes player move downwards.