Here's to hoping someone will know what I'm looking for based on this very vague memory I have:
It's an old(er) show. I think my brother and I caught it on the old Scifi back when they occasionally aired anime (Iria: Zeiram the Animation, Armitage III, etc.), so probably form the 90's. All I really remember is an airship. At least, I think it was an airship. It may have just been a regular ship. And the crew of said ship was headed to a cave (may have been in the mountains, which is why I was thinking airship specifically), in search of... a crystal? Something to do with the four elements, I believe. Beyond that, I have no idea. I can't recall if the crew was made up of adults, kids, a mixture, robots... nothing. Sorry for the lack of information.
Thanks for taking the time to look at this!