There is a weird splashing sound on loop sometimes when the player goes underwater and the fish are acting strange.
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I had the same thing happen to me multiple times while crossing an ocean full of fish. Also worth noting; the sound is unaffected by by the volume level. It's the same unless set to OFF.
Confirmed on 20w12a
The odd behavior is still around in 20w13a. There were a few fish I found on the riverbed spinning in circles and unable to move.
Could possibly relate to MC-165802?