If the goal is to protect the pump, one of the submerged flow switches is enough.

If having mains voltage in a submerged wire is a problem, you can run the switch on 12V DC from a small power supply and use a 12V relay to control the pump.

If you want visual level indication... personally I'd go with analog.

On the well pump, I use a flow detection switch. Here's an explanation of how it works.

When water is needed, the pump turns on, and a timer starts. After about twenty seconds, if the flow switch does not detect flow, it automatically turns off the pump and it will remain off.

Unlike water level meters, this also saves the pump when the inlet filter is clogged...

These aliexpress paddle switches can also be used as a rugged version of the microswitch to build jonathanjo's solution, or as a limit switch for the above "analog" solution. You don't have to screw them into a tee on a pipe. You can also use it as a switch by replacing the paddle with a float or having something that goes up and down with water level bump into it. They're pretty robust, enclosed, have 15A contacts, and the pipe connection is obviously watertight.

If the goal is to protect the pump, one of the submerged flow switches is enough.

If having mains voltage in a submerged wire is a problem, you can run the switch on 12V DC from a small power supply and use a 12V relay to control the pump.

If you want visual level indication... personally I'd go with analog.

On the well pump, I use a flow detection switch. Here's an explanation of how it works.

When water is needed, the pump turns on, and a timer starts. After about twenty seconds, if the flow switch does not detect flow, it automatically turns off the pump and it will remain off.

Unlike water level meters, this also saves the pump when the inlet filter is clogged...

These aliexpress paddle switches can also be used as a rugged version of the microswitch to build jonathanjo's solution, or as a limit switch for the above "analog" solution. You don't have to screw them into a tee on a pipe. You can also use it as a switch by replacing the paddle with a float or having something that goes up and down with water level bump into it. They're pretty robust, enclosed, have 15A contacts, and the pipe connection is obviously watertight.