Here's the thing.
IP68 means that the device is rated for complete protection against dust (it is dustproof) and is able to be immersed in water beyond 1m (in the S7's case, it means it will be fine in water up to 5m deep, or about 16-feet of water). However, note that I said "immersed". If you look at a phone like the XPERIA Z5, it's also rated at IP65 alongside the IP68 rating. That means that it is not only rated as dustproof and water-immersion resistant. It is also resistant against water jets of a certain pressure, like a faucet. The S7 isn't rated for water jets, so placing it under a faucet isn't a good idea.
Also note that Samsung keeps mentioning "water-resistant" several times. That's different from "waterproof".
In short, it's more for accidental spills. It might be fun to show off to your friends in the washroom sink, but please don't go overboard unless you really know what you're doing. That said, it's fun to take to the pool for a second of immersion when you want those cool underwater photos. Just don't put it under a faucet.