After getting the watch wet you should clear water from the speaker. From the Manual:
https://help.apple.com/watch/#/apd36e57e00c
Go for a swim. With Apple Watch Series 2, there are two swimming workout options. When you start a swimming workout, Apple Watch automatically locks the screen with Water Lock to avoid accidental taps. When you’re done, turn the Digital Crown to unlock the screen and clear any water from the speaker. You hear sounds and may feel some water on your wrist.