If your watch has no damage, get a bowl of warm distilled water (not tap or spring!) carefully take off the straps and place the watch into the water. Let it sit for a few minutes and pull it out press the water drop from the control center then rotate the crown to enable the cleaning cycle which will engage the speaker. You may need to do this a few times to get the junk moved out.
Reference: [https://support.apple.com/en-us/HT210931|How to use Water Lock and eject water from your Apple Watch]