Summary:
Shift swimming (MCPE-166565) on blocks fills the player's first-person screen with a block texture.
A possible solution could be to prevent the player from sneaking while swimming. Playback methods may vary depending on the control.

Steps to reproduce:

1. Hold Crouch while being underwater.
2. Start swimming.

Observed results:
When you swim on blocks, the first person screen fills with the texture of the block.

Expected results:
The screen will not be covered by the block texture while swimming.

Video:
Shift swimming.mp4