ESD Protection Necessary for Water Detection Circuit?
The CD4093 does have ESD protection. There are diodes from the inputs to power and ground and a small series resistance. The CD4093 also has characteristics that are important for your application but lacking in the 74LCX00: it will operate at 12V and it has Schmitt-trigger inputs.

If you are worried about ESD you could add your own diodes from the sensor terminals to ground and to the 12V power supply. The diodes should be oriented so that if the voltage on one of the sensor terminals goes above the power supply voltage then one diode will conduct (this diode has its anode at the sensor and its cathode connected to the power supply), and another diode will conduct if a sensor terminal goes below ground (this diode has is anode connected to ground and its cathode connected to the sensor terminal).