Let's put this in its proper perspective. I am not an active geocacher, but I know many who are and I have visited several of the caches and the national (and international) websites that log the data associated with them.
Geocaches are not items simply "dumped" in an area to attract attention. Rather, they are small, nondescript little "troves" of minute items (sometimes only a notebook to log the "finders") that can be taken or exchanged by the persons who find them. If you were to put a proper geocache on my front lawn, ideally I would not even notice it. Persons looking for the cache would need to follow a set of clues beyond the listed coordinates in order to locate the cache. Obviously, no one is advocating what you evidently envision this activity to be...the widespread scattering of debris and junk over wide areas of pristine environment. And, of course, no one is advocating the breaking of any laws (trespassing, un-authorized placement of materials in a National Marine Sanctuary or other government land, littering laws, or other rules). After all, dropping a 200 foot derelict ship on the bottom of the sea is, in essence, mega-geocaching, but that requires a LOT of permission-granting and regulations. The only real difference is that the shipwreck is in plain sight and much easier to find!