One of the features that Samsung removed on the Galaxy S6 was the water and dust resistant hardware found on the Galaxy S5 thanks to its IP67 rating. The company made such a move in favor of an improved design on the Galaxy S6 and for the first time, the company used premium materials on its construction. The strategy worked quite well, but this year, Samsung managed to keep a premium design and build-quality while also making the Galaxy S7 and Galaxy S7 Edge water and dust resistant thanks to their IP68 certification. Samsung has been advertising this feature in all sorts of ways, from illustrations of the phone with some drops on it to an underwater unboxing video of a T-Mobile Galaxy S7.
Now, a user from XDA Developers named xxaarraa, mentioned that he took an underwater photo with a Galaxy S7 Edge and tried charging it 4 hours later, but there was an error message regarding moisture being detected on the charging port, so the phone wouldn't charge. A little later, he tried drying the charging port with a hair dryer but the phone still wouldn't charge and the message didn't appear anymore. Unlike some of the first phones that featured water resistance, the charging port on the Galaxy S7 phones is not covered, so any droplet in the port while attempting to charge them could lead into some kind of damage.
The error message and not being able to charge the phone after a while could mean that Samsung integrated some kind of sensitive safeguards into this port in order to avoid further damage, it could even be possible that the software is programmed to prevent charging for a couple of hours after detecting moisture. A few hours later, the user reported that the phone is charging again, but even when plugging it to a charger with fast charging capabilities, the phone is charging at regular speeds. Even though the phone is said to be water-resistant in up to 5 feet of water for up to 30 minutes, it would be better to avoid using it under water, as some companies have been changing their warranty policies towards water damages on phones that are advertised as water-resistant.