I hope this is applicable to this section. Basically I have two hydrophones immersed in a water bath, approximately 12cm apart. One is connected to a function generator, the other to an oscilloscope. I'm comparing both the transmitted and received waveforms on the scope, but I'm finding it difficult to explain my results. Basically my observed waveform is at best in phase with the input, and at high freq (~100kHz) actually leads the input signal on the scope! Doing a basic v = s/t, and taking the accepted value of v=1482m/s, I reckon I should be getting a Δt of 80μs between the waveforms. Have I broken physics??