Very pleased that my second attempt at a DIY hydrophone finally worked. It was late at night and the only thing I could find that could make some sort of interesting sound in water was an old can of ‘Pokemon’ themed fizzy drink.
Below is my working DIY hydrophone!
The piezo element is glued to the metal backplate of a repurposed wristwatch. I chose very thin wire to connect to the cable and 3.5mm jack so it could be passed through the small hole where the dial used to be. I superglued the glass top onto the backplate to ensure it is watertight, even though some water still manages to get inside.. Still, this is still very usable and way better than what I was working with previously.