The "water light" in a 2000 Honda CR-V comes on when the coolant level in the radiator is low or when the coolant temperature is getting too high. In either case, this light comes on as a warning so that you can stop driving so that your engine won't be damaged. When you see this light, pull over and park your car so that the engine can cool down. Then, check the coolant level and add more coolant if necessary. Check your owner's manual for instructions on how to add coolant. Once the coolant level is where it should be, you can also start your car and let it run for a few minutes, at which point the water light should turn off.
If the water light does not turn off even after running your car for a few minutes, it is best to take it to a mechanic to have it looked at. This could be an indication of a larger problem with your cooling system, and you don't want to keep driving your car like this because it could lead to the engine seizing up and your car being totalled beyond repair.
