thank you for the answer.
I was not sure about it the whole hole. Reworked it.
In the scene, the mid part is surrounded by water now.
Some holes do have very clean water which looks teal. Volume absorbtion shader does good job together with transparent shader.
For some reason, the glass-bsdf renders way too dark. Trying workarund – add glass-bsdf and transparent-bsdf to lighten it.