Correct and yes the additional dock is required. Very expensive in the end though a nice sensor.
@jpoeppelman1 if you are a tinkerer you could make your own using @ogiewon’s Hubduino libraries. I was going down this path but unfortunately there aren’t a ton of water probe sensors available that met my criteria but a 2 conductor wire could work. I started out just buying the Aeotec Water Sensor 6 usb dock as it came with the probes but they wouldn’t work with 3.3VDC voltage reliably from my ESP board. I ended up buying the Aeotec sensor since I needed a very reliable sensor for my sump pump.
As others mentioned there are “battery eliminators” available where you can turn a battery device into DC powered. I’ve made my own using a wooden dowel:
