Hi.
I did a job a while ago where we needed to measure the level of water in a bore. We dropped a 6 mm open end tube down the well and connected a pressure transducer to the tube at the top of the well. We then connected a small air compressor to the tube that maintained a pressure in the tube. Not sure how it worked but we were able to get the depth of water in the well from this transducer. (remembering that the air pressure in the tube is limited to what air can escape the open end of the tube which is at the bottom of the well)
This is just out of our comfort level. I know other people have done this in the past and I'm not willing to re-learn the things they have on such an application.