The important thing is that it is a wave, what the wave is composed of does not affect the maths of the Interferance and reinforcement that goes on to make a beam.
However you have not said what you want to do with it. Is it a cave survey sort of thing?
Where in the UK do you cave. I did most of mine in the Youkshire Dales but I have been to the Mendips and to Southern Ireland and the charastics of the caves are very different in all three places.