Strange resurgence

In this pond, where water is very calm and clear, there's an underwater resurgence. It provokes a small mud geyser. I put a microphone inside. It's simply astonishing ! No, it's not an old gramophone record, it's not the sound of my feet when I'm driving by bike like a crazy, it's not a bowel movement... It's an unmodified sound underwater of a strange resurgence inside the mud. Why is it like that ? Perhaps an pressure coming from the nearby river ? Unfortunately no explanation.