[Hardest/Most Remote Cache]

As I understand it there's a rule about no cache being commercial. The ocean cache doesn't say that you must use a particular service to get there, just that the expedition is one way; admittedly it's the easiest way, but there are other options. A good example would be caches that are on hikes that require adventure passes. Those are alright, because you don't have to use the provided parking, it's just an option.

[Geohashing, XKCD style.]

This comic is actually the very thing that led me to geocaching. I wish I'd have known earlier, it's so much fun.