When you put the hydrophobe in the river and then in the creek what you heard is called flow noise, the water passing over the surface creates all the noise. This is what you would hear with a professional hydrophone.

If you use one of the diy pre amps designed for piezos, even the basic ones you can get good results. I meg impedance is what's needed to stop the low cut filtering effect. Piezos get a bad rap. Piezo tweeters are excellent quality sound, I know I hear folk complain they're tinny, but because they're cheap and can be used without a crossover pcb, with a low mid speaker, a lot of manufacturers do this. If paired with a crossover they only operate in their optimal range and deliver a better sound.

The problem with contact mics is that they sound bad, so the next step is learning to create a circuit to low down impedance and make them sound much better. Good, vídeo

Really great tips with the DIY mic and Plastidip. Cool to hear the sounds you collected. Thanks for the vid!

Super cool! Kinda need to pee now.

If you talk underwater, (the best you can) or yell, this pick up the sound, right? That sounds pretty cool. Sound travels quicker through water, would this spot/record the difference? Cool video! Cool shirt! And @5:24 lol Keep it up Cuz!!