Hi @Darno, sorry to hear about this. 
Do you still experience this behaviour is it better now? There might be tiny water droplets covering the nets after the phone is taken out from the water. This affects the propagation of sound in the air, which causes the sound to become smaller. In the ordinary environment, the tiny water droplets may evaporate naturally within three hours, so that the phone then can be used with normal sound performance.
Let me know if anything has changed!
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