Don't do it...unless you have a real good idea of what job you want and you NEED a degree to get it. In a job interview experience usually trumps education. If you just want to party for 4 years, get a job delivering pizza(what I did in college, cash in hand every night was nice...) or something on campus and just walk into random classes until you hear something you like. You'll learn just as much and won't have any loans to pay back, but you won't get a fancy piece of paper. I went for an associates degree and worked in that field for 3 years only to go back to what I was doing before I went to school, CNC machining. I get better pay, more vacation and better benefits/insurance, plus the company I work for now doesn't seem to believe in working hard, it's the easiest job I've ever had. If you REALLY want to go to college, go, it's not always a bad idea, I had fun but I'm still paying for it...
Sounds like you're already good at what you do, try to get a job now and see how many people in the interviews say you need a degree. You'll start off at lower pay, but 4 years experience will get you more money than no experience and a piece of paper.
I think it all depends on what the OP really wants to get into, and after he does his research he can make a decision. Not trying to argue with you, but there are a lot of factors that go into it. Most people that don't have some type of degree (Associates or Bachelors) - aren't going to easily find a good job like you did.
Again, I was lucky in that my parents paid for my education. My dad has worked in an auto factory since he was 19 years old, and he worked 7 days a week from the time I was about 10 until a couple years ago. At least 15 straight years of working 7 days per week, to get the overtime to pay for my sisters and I to get an education and not have student loans out the ass. My 4 years + that piece of paper started me at $50k right after I graduated. All circumstances are different, but of all of my friends back home who didn't go to college - there may be a couple who have decent jobs but most of them are still working the same random jobs they had after college. My degree allowed me to work for a Fortune 10 company in Michigan for 3-4 years, and then allowed me to move to Colorado for a better paying job right near the mountains. I don't think I would have been able to do that without a degree.
Seeing as this is a Snowboarding forum, Marine Biology doesn't really fit into the plan very well. There aren't too many places that you could be a Marine Biologist and also be close to the mountains. PNW maybe? A similar job you could look into would be a DNR (Dept. of Natural Resources) agent, where you are out in the wilderness all the time.
The cool thing about Graphic Design is that you can do it from ANYWHERE. There are design firms everywhere, or you can freelance and work from home - which could be at a condo at the base of a mountain if you wanted. The only thing is... you better be pretty damn good if you're going to freelance.
Speaking of which... why don't you post some of your art here?