All sorts, possibly. I don't know how true it is, and things may have changed since I heard this anyway, but it's been suggested that we know more about the Surface of Mars than we do about what's under the sea. (Bill Bryson, "A short History of Nearly Everything").
I watched a programme about the Antikythera a couple of months back.
It was simply astounding that such precison, accuracy and craftsmanship was possible some 2,000 years ago.
I hope they find what they're looking for.
Trying to find some small bits of encrusted brass in among all the other junk won't be easy. This site has been searched several times since its discovery, last time being as recently as 2012, by divers using re-breathing scuba gear.
According to the article on the same subject in The New Scientist, the suit allows divers to submerge and return without depressurisation. Divers in this suit can come up immediately.