I want to explore space or the ocean, do digital art, or work with animals. I need to decide soon; I'm about to start my adult life and I want to have some idea of where I'm headed before I set out. Help?

The best way to help make a decision, is to take classes that would further your education towards those goals.

If you find you don't like the education, chances are you won't like the career.

Talk with some people who actually work in those (rather diverse) fields.