'Water weight' is most often referring to two things:
glycogen stored in muscle (ie. energy source for muscles, comes from carbs - glycogen binds with water)
blood and cell volume (moderately affected by sodium/potassium mechanism, but more importantly hydration)
Under normal healthy circumstances, people don't usually have 'water retaining' issues (eg. swollen lower legs).
However, if you start to follow a lower-carb eating pattern, your body will most likely use the glycogen stored in your muscles in the first week or so, while failing to replenish - decreasing the amount of water being 'stored' in your muscles as a result. This is usually what people are referring to as 'water weight'
Your body is pretty darned efficient at regulating it's sodium levels, so I generally don't worry about salt all that much. However, it is important to stay hydrated! Drinking less water than you lose (through perspiration, breathing, excretion, etc.) will also result in losing weight, purely in the sense of lbs off the scale. But it is a false loss, and you are much better off to remain well hydrated. Just as you're doing; kudos!
If you haven't experienced a 'whoosh' beginning with your change in diet, it doesn't mean that you're not doing it right! Everyone reacts a bit differently, so try not to overthink it. You're much better off to focus on long-term fat loss (and possibly gaining a bit of muscle, if that fits with your goals).
Best of luck, have fun!