It means that you either have a wire loose on the reservor or need to add some coolant to it. It should be located on the right front fender. There is a wire plug on the bottom, if it is loose it will show that you need some coolant. Yeah, a water down symbol would probably indicate low coolant? Anyway, gotta love the days when GM used lights that actually said "coolant low" instead of stupid symbols.
low coolant
this means that you have a low coolant level
Engine coolant.
brakes, lights, oil, water, battery, air & gas
if the water and oil levels are fine, then you may have a sensor going out
That light is a warning that your engine coolant is low. Check your expansion tank for the proper level and fill as necessary.
engine is overheating, check coolant level. DON"T open radiator when its hot.
That one is low fluid level.
low coolant (antifreeze) Make sure the engine is cool before you open the cap and top-up the cooling system.
why does my 2002 chevy cavalier over heat after i change the thermostat and the water pump
To answer you question more thoroughly I will need more detail because there are several different types of water qauges. You have a water temperature gauge, water pressure gauge and water level gauges.
If the cooling fans were working and all the hoses and water pump are not leaking coolant I would suspect the head gasket and/or a cracked head is very possible. You need to have the cooling system pressure checked, this will help determine the cause of the coolant leak. I wouldn't run the engine anymore at this point, if coolant is mixing with the engine oil it would be the end soon.