I would suggest considering the borehole measurements as a vertical profile. In terms of the CF Convention it would be a featureType profile, which is described in the discrete sampling geometries section.
I didn't include all reference to the relevant sections in the CF Conventions below. Just comment if import things are missing.
There are multiple ways one can look into this. For example, one simple way of increasing the length of coastline and, thus the beach area, would be to expose all of continental shelf.
The shelf break, where the continental shelf ends is pretty uniform globally and is in most cases at a depth of 140 m. As such, lowering water level by this amount will ...