Be warned: it is extremely difficult to make a living in marine biology. You better have good grades, a strong work ethic, and shake a lot of the right hands if you want to make it. Basically unless you're completely obsessed, I wouldn't recommend it, and even then I still kind of don't. If you do a quick search on indeed.com, monster, or any other job posting site you will quickly realize that there are VERY few positions in this field. About 50% of the people I graduated with never made a dime in marine science.
I don't want to be mean or discouraging, but you should seriously think long and hard about the reality of spending $50,000 on a degree for which there is almost no decent employment. Unless you are willing and able to prove that you are the best, it's a bad idea.
On the bright side I've been working in the field for 7 years. I started at the aquaculture research center of UNH when I was in college. From there I did some short temp work at Great Bay Aquaculture. When I graduated, I went to Alaska to work as a fisheries observer where I saw some of the most incredible things in the world (like orcas 5ft away creeping on our boat while we fished half a mile from a visibly erupting volcano). After four years in Alaska, I met the right people in my company and was able to get a job in electronic monitoring where I install camera systems on commercial long liners so we can track bluefin tuna bycatch on the east coast. I made it, but it was a hard road. And I got really lucky in a lot of ways, such as meeting the right people at the right time, and surviving several situations where I really thought I was actually going to die in the Bering Sea.
If I still haven't turned you off from marine science and if you only remember one thing from this post, remember this piece of advice: When you get to school, find a professor studying something you're interested in and volunteer in his/her lab. This might make you some money and more importantly it will get your name in scientific journals which is extremely impressive to future employers.