Water level indicator LEDs one by one
This can be achieved fairly easily with the help of a microcontroller and a bit of code.
You can use an Arduino which is quite easy to start with.
Connect each Led to a pin of the Arduino and use what is called a PWM to vary their frequency.
Connect your sensors likewise to other input pins.
There are tons of example on Google on how to achieve that, they keyword is LED PWM control Arduino.