When I get water deposits from hard water on my glass shower door I take some vinegar and dilute it with some water.
The way I do it is fill a spray bottle halfway with vinegar and then fill the rest of the bottle up with water and then shake it up to mix the Vinegar and water together.
I then spray the Vinegar and water solution onto the shower door and let it sit for at least 10 minutes and then I scrub the water deposits off.
I then go a second time around spraying the shower door with the vinegar again and then wipe the shower door off with a cleaning cloth.
Then I go another time with plain water to rinse the vinegar off the shower door.