Ultrasonic sensor

I am here in search of a non-contact water level measuring sensor with 1mm level accuracy with sensor fixed 1.5m from water surface in a 10x5 meter water tank and  water depth is about 3 meters. I want to do Dynamic wave height measurement  when waves occurred in the water tank. Please advise from AD ultrasonic sensors and  what are the methods(i.e. Filters) need to be followed to eliminate the noise on received data from ultrasonic sensors . I am new to this ultrasonic sensing, Would be of great help if the design reference for the same can be shared.

Thanks

Rao