I presume you mean a coolant leak, rather than freshwater.
The collant pump is on the front of the engine (behind the cambelt cover) and they are prone to the front seal going, resulting in a slow drip from the pump which runs down the front of the engine and drips into the bilge.
The only solution is to replace the pump. Unfortunatly pattened are getting scarce now and VP ones are about £300.