Mix toothpaste with baking soda to form a thick paste. The toothpaste should be the white paste type, not a gel toothpaste.
Rub the mixture with a damp cloth in a circular motion on the water mark. You will start to feel the mixture getting warm from the friction of the rubbing and start to see the stain fading. Continue rubbing in a circular motion until the spot disappears.
Wipe the area clean with a damp cloth.
Repeat the process on each additional water spot.
Wax the floor to restore shine.