Apple Watch Noise is not working well.

There may be water in the device still- make sure you eject it after your activity. To do so, turn the Digital Crown on the side of your Apple Watch until the display says Unlocked. You can rotate the Digital Crown in either direction. A series of tones plays to clear any water that remains in the speaker, and then you can use your display as usual.

How to use Water Lock and eject water from your Apple Watch - Apple Support

There should be some sort of water lock mode or something. Are you using that?

because it should eject water with sound waves after you turn the mode on.