Sadamune:
I love it!
When I was at CAL the "environmental studies" stuff happened in the Department of Forestry in the College of Agriculture. That was the "mick" path for those who found that they were not cut out for the more demanding Zoology, Biology or Botany programs. This may not be true today, that was a while back.
If one is interested in marine sciences the first decision that you need to make is do you want to be a "Marine xxx" (where xxx = Biologist, Chemist, Geologist, Botanist, etc.) or an "Oceanographer." Oceanographic programs expect you to be competent in four marine disciplines, Biology, Chemistry, Geology and Physics and specialize in one of the four. They tend to be more "integrative." "Marine xxx" Programs tend to be more tightly focused and specialized and can even be just your own custom tuning of your course work to the marine world.
I suggest (as an Oceanographer) that anyone moving that way do, at least, majors math through linear algebra, the major's lower division series in Chemistry, Biology, Geology and Physics, Basic Statistics, Exploratory Data Analysis, Experimental Design, a survey course in electronics, a survey course in microprocessors and an introductory course in mechanical engineering. Major in the field that you're most interested in. That's a five year program, not four, and you'll still need to go to summer school to get it all done.
While your at it, take the research diving course and hand around to help teach it, learn to handle small boats, fix outboards and small marine diesels, troubleshoot marine electronics and learn to speak at least two foreign languages.
Do this and I promise you that you will spend the rest of your life being paid to go incredible places, do incredible dives and have someone else buy all the toys that you'll ever want and let you play with some that no one except Paul Allen could ever afford alone.