I've been working on a citizen science version of this, we have 7 hydrophones deployed that anyone can listen to live:

https://live.orcasound.net/

These hydrophones are a bit more expensive (~$1k per deployment) but still very accessible compared to how much it usually costs. And the goal is to bring the cost down to the ~$100 range (so $5 is very impressive!):

https://experiment.com/projects/can-low-cost-diy-hydrophones...

All the data is being saved (used for scientific research & ML training), with some of the hydrophones going back to 2017, and yes it's quite difficult to listen to and review so much audio. Better tools like the hydrophone explorer UI are much needed (been working on something similar).

One of the things that's surprised me the most is how difficult to keep hydrophones up and running. I can sympathize with both the technical and social challenges—underwater is not a friendly environment for electronics, and it can be difficult to get permission to deploy hydrophones. But it's incredibly rewarding when it works and you capture some cool sounds.

For anyone interested, all the code is open source and acoustic data is freely available:

Code: https://github.com/orcasound/

Data: https://registry.opendata.aws/orcasound/

Community: https://orcasound.zulipchat.com/