As of updating to 1.20.30, mob splash sounds seem to be much louder and may be incorrectly using the player entity splash sounds. This problem is amplified by the fact that many mobs will jump excessively in water. This makes playing with any mobs in water quite frustrating as they will create a cacophony. Ideally, reducing the volume of these sounds, changing the sounds made, or giving players the option to control the volume of these sounds should solve this problem.
Steps to replicate:

• Spawn into world
• Locate a body of water
• Place non-aquatic mobs in water (llamas, wolves, etc.)
• Listen to sounds played and their volume