A few simple checks first
There are a couple of simple checks you can do to determine the source of the water.
1. Leave the car parked overnight as you normally would. Before driving off next day, look to see where the water is sitting in relation to the car. Is it under the radiator, or further back around the transmission? Up front could be a rad leak, further back will be the air con>
2. Do you have coolant in your cooling system or only plain water? If you have coolant, what colour is the water on the floor - same colour as your coolant, or clear?
3. Do you have to keep topping up your header tank?
4. If all evidence points towards a coolant leak, check all hoses, particularly heater hoses where they join the water pump, the pipes through the bulkhead and other connection points. Hoses that are swollen and soft immediately adjacent to the connection points are weak and possible leak points. They could also be about to burst. If swollen. cracked or even hard and resistant to squeezing, replace them. Some hoses become hardened with age internally and lose their pliability. When you squeeze them you can feel the hardened core of the hose breaking up.
If none of these checks eliminate your problem, then the water pump is the next possibility. There is a weep hole under the bearing behind the pulley, which permits water to drain when the impeller bearing seal has failed. Once you start to get leaks from here, it's time for a new pump as the bearing will kark it before long.
Finally, if all else fails, have your system pressure tested to see where the leak is.
Good luck - hope its one of the easy ones.
Regards
pj