>>1562139Cool ideas man! The larvae will definitely be a challenge but totally worth it if you can pull it off. With the hydrophones I imagine the preamp will be really important to how sensitive and noise-free they are.
I made mine with a couple piezo guitar pickups (just snipped the plastic clips off and removed the foam pads and then Plasti-Dipped the whole thing to water proof them). They do have a bit of a ring to them being hollow plastic discs but since decent hydrophones are a couple hundred bucks it was worth it for me. The real trick is the preamp - piezo discs have a really high output impedance so you need something with an appropriate input impedance otherwise it sounds noisy and tinny and cheap. After day searching for something appropriate I came across the Behringer Acoustic guitar DI for like $30. It has a stunning 4.7MΩ input impedance (impossible to find anything else for under $200) which makes the piezos super quiet and have lots of rich low end. A little EQ in post helps take the mid-range ring out of them. I would love a pair of Aquarian hydrophones but just can't justify it, seeing how little I need them. Plus my piezo ones are better as contact mics as well which is also worthwhile. All up my contact/hydrophone setup cost about $70 rather than $400 and it's probably about 3/4 as good (well, maybe). I have a little box that houses the two Behringer pedals and I can basically strap it to the tripod and plug in all the cables without having to even open it.
I don't really have any interesting bodies of water around me anymore sadly
