Water spots on windows on houseboat will NOT come off! Things I've tried:

windex
fantastic
X-14
Lime-Away
amonia
Meguiars Cleaner Wax with an orbital buffer (this works a little bit)
Turtle Wax Polishing Compound (works, but must work on a small spot for a
LONG time)

It's tinted glass - real glass, not plexiglass. The Meguiars wax on the
electric buffer has given the best result/effort ratio so far, but still can
see a lot of spots when the sun hits it just right. With the Turtle Wax
compound I would be able to get off all the spots - by Christmas! But the
Motrin bill would bankrupt me!

Surely there is SOMETHING that will cut these spots off relatively easy???

Any ideas are greatly appreciated.

cag