I’ve done a lot of hydrophone recording in various environments and bodies of water (rills, rivers, lakes, shore, blue water),
and this is a crummy recording in every respect, the methodology is god-awful, and there is absolutely nothing in this that is mistakable for a “heart beat.”
I have used hydrophones to record heartbeats and there is zero—zero—chance you would get a recording of even a very large animal’s heartbeat from the open water.
This is the junkiest of junk science. You should’t amplify this stuff, without clear /s
