How do I tell if an Apple Watch's water resistance has worn out

I recently bought an Apple Watch series 4 used online. I was reading about the watch's water resistance, and found the following sentence on the Apple website: "Water resistance isn't a permanent condition and may diminish over time." I have also heard water resistance can be damaged by being taken apart, or exposed to chemicals. How can I tell if the water resistance on my used watch has already worn off? The watch is, at most, a bit over two years old (because of when the series 4 came out). So is this something I should even be worrying about at that age? Thanks!