First I assume you are not talking about the formal “2-wire” interface which the EZIO2X4 does not have an Input that supports that interface.
Really need more detail about the water sensor. Water sensors have been problematic over the years as they are dependent on the resistance of water which varies widely by water source. Smarthome sold one variant and finally discontinued it because it was so unreliable. Can you provide more detail on the actual signal levels the water sensor provides. The EZIO2X4 has two opto-isolated Inputs which can handle 12v DC. Need to know the actual voltage levels the water sensor will present both wet and dry. Who is the manufacturer and model number could be useful if they provide information online.