Quick Introduction:

This is a rendering bug. This is a bug which causes weird rendering of banners through water. This bug is not affected by any of the video settings.

Images:

Below image is from Windows 10:

Below image is from Nintendo Switch:

Below image is from Android:

Conclusion:

This issue is on both Windows 10 and Android, but somehow not on Nintendo Switch.

Screenshots were taken from: Bedrock Dedicated Servers and Local World (Realm not tested)

All screenshots are from the latest version of the game(1.19.20).

(I did experience the same bug on 1 preceding version of the game)