I was fascinated by the Winterwatch programme where a Lesser Water Boatman was recorded using a hydrophone sliding his penis over his abdomen to try and attract a mate. This was also recorded using a hydrophone at 3 locations 29.1.23. There was still ice in the pond although it wasn't apparent at first and when it made contact with the contact mic there was a graunchy noise (especially towards the end). Note the Great Tit calling at the beginning and insect activity after 1.00 minute for 22 seconds. I couldn't tell if it was a Lesser Water Boatman but it sounded very similar.

Hydrophone 2 Hogsmill Nature Reserve Pond with Ice And Great Tit

Benton Bat