Ground Plane Default Height

Just curious as to why the default ground plane is 32 m up. I thought it was basing it off of sea levels, but the ocean is 16 m up, instead of 0 m.

I have found that the ocean floor (not the water surface) is hard-coded to 0m. I suspect this is why the original programmers made the ground plane default up around 32m. If you try to push the ocean water surface too close to or below 0m, there are visual artefacts.