Pushing the boundaries of the unknown is a concept many of us are attracted to. 

In the case of cave diving, the end might never be reached which means that you have the opportunity go where nobody has gone before. With cave systems all over the world being discovered, explorers keep learning new things. For example, some of the wildlife found in dark caves may have never evolved to have colored skin, as camouflage in the darkness is not very useful to their survival. 

Some of these species have also never evolved to analyse electromagnetic radiation, therefore they are blind.

Concepts like these make us discover new things about earth and the precious life it holds.