There are two main types: digital water thermometer and analog. Which one you choose is entirely up to you, and both come with advantages and disadvantages. Analog thermometers are the thermometer you will be most familiar within this world.
The analog option will be able to deliver results and measure the water temperature, but since they are built for simplicity, you aren't supposed to expect highly accurate results. On the other hand, when using a digital option, you will be able to read the results and make sure that they are seen perfectly clear, which won't always happen with an analog option.