We know by now that adding ice to scotch is not the recommended route to take if you truly want to appreciate the raw character of the whisky (read here), but what about adding water? I have heard varying opinions on whether to add water to your scotch. Some prefer to drink it neat, some with a splash of water, and even others who drink their scotch with an equal mix of water and whisky.
Generally, it is true that adding a few drops (literally, a few drops) of water can "open" the whisky. What this means is that the water can help release the aroma (or "nose") and flavor from the drink. Some also add water to their scotch if the flavor is too bold, and they desire to reduce the intensity a little.
Overall, there is no hard and fast rule about adding water. It all boils down to personal preference. Personally, I seldom add water to my scotch with the exception of the real peaty ones.
If you are undecided whether to add water, do not be afraid to experiment! A big part of the appreciation of scotch is the never-ending journey of self-discovery. Trying drinking the scotch neat first, then add a few drops of water (preferably at room temperature and filtered) to it and decide for yourself which one do you prefer.