An underwater surveying class that was practising mapping out a cave finding an unmapped passage doesn't really fall into the concept of "accidental discovery"

An underwater surveying class that was practising mapping out a cave finding an unmapped passage doesn't really fall into the concept of "accidental discovery" to me. For sure it was a lucky discovery because they weren't especially looking for new passages, but it can't really be said to be accidental in the sense of the vela satellites detecting GRBs for instance.