Thanks!

The old Traveller hex maps were quite seductive, and I was tempted to use them, but in the end they are just way too unrealistic for me. They're great in that you can easily map a vast territory. However, once you add 3d information, you'll also have to make the data 3d - that is, you actually have to have a lot more systems in the same x,y coordinate space, and those hexmaps suddenly become very very unwieldy.

The 2300AD map used size-variable icons to indicate z-axis, and it's quite a beautiful map. It only covers a sphere of 50 ly though.

As for water, incidentally, it may be less common on some worlds than on others, but I kind of have my doubts there'd be solar systems without any water at all. Spaceport codes may indicate accessibility though.