Not sure what you mean by "one" but a watch will work fine without a network connection. It does need to be paired to a phone.

It'd make it less useful as a watch though because the time will drift without an NTP server.

I don't think this is true? All my Apple Watches refuse to provide any functionality at all, including just telling the time, until I pair them with an iPhone. This was an issue when I bought my first Apple Watch because I owned an Android.