I leave my apple watch on a charger for at most 15-20 minutes in the morning and that gets it from the 10-20% in the morning to about 80-90% which is enough to go the whole next 24 hours even with a 30 minute lunch walk and 2-3 hours of pickleball fitness tracking as well as having the always on display on.

Never once has this seemed like a problem or that I would want to wear my watch in the shower for some reason. It's shower plus getting dressed and brushing my teeth etc.