You definitely need to have a solid background in math. The better you are at math, the better marine biologist you can be. Now do not let that worry you. If you really want to be a marine biologist, you'll work it out. Sometimes, you just need to find the right teacher to make it more understandable. I'm sure you can do it. I'm a marine biologist. I've got a site, mylifeasamarinebiologist.wordpress.com designed to answer questions just like this, to give kids an idea of what it's like to be a marine biologist. I think following it will give you a good background to get yourself ready for your career.