[dmd]

The delta-v from Earth Surface to the bottom of the ocean is 0, so by your logic, going there is trivial.

[OJFord]

Well when did you ever hear of a space agency bothering?

Jokes aside, I hadn't heard the term before and from what I could guess/infer didn't see how it could be a measure between two places: https://en.wikipedia.org/wiki/Delta-v

[crubier]

It’s a measure of the energy needed to move from one orbit to another.