Yes, you can wear Galaxy Watch 6 in the shower. There is no harm in wearing it in the shower for a few minutes or half an hour. As per Samsung specifications, the Galaxy Watch 6 is capable of surviving in freshwater like the shower, swimming, or washing hands. It comes with IP68 water resistance technology that is rated to survive to watch up to 5ATM water and dust resistant. Further, it is fine to use in a swimming pool for 30 minutes and up to 1.5 meters deep.
It doesn’t mean you can use Galaxy Watch 6 anywhere. You have to be more cautious around seawater because it doesn’t give any guarantee about salty water. Some users claim they used their Galaxy Watch in seawater, and the watch is just fine. There is no need to check it for yourself, just use it in freshwater. In any case, if the watch becomes faulty after using it in normal condition, then you can visit the service center.