I work with a lot of Marine Biologists. It's 90% of my life supporting their efforts. Here is what I see.
Everyone wants to be a marine biologist, because dolphins are cute, sharks are fun and scary, and whales have a certain wow factor. Guess what? Sponge and algae need love too, but no one wants those jobs, because they don't involve cute sea creatures.
Starting jobs for BS Marine Biologists are aquarium cleaning, Disney if you are lucky and good looking, and asking if you'd like to supersize that. Internships for MS and PhD students include summer research cruises counting fish, performing benthic surveys, and working in a coral nursery, and maybe netting in Florida Bay for starfish. I know of a few masters graduates who make far less than I did with my high school diploma, and if you want a real job paying $45k a year, you will have to have a Phd. I know of one Marine Biologist working in an FTE position for FFWC who cannot get accepted into a PhD program because there just isn't room or funding for the slot. She has 2 master's degrees. Her grades were Dean's List for both Masters. She can't get a slot in grad school for a PhD. Granted, she is only looking in Florida, Rhode Island, or California.
Your alternative is to do something like I did. I joined the Navy, got my Engineer's Merchant Mariner's license, also my Captain's license, got a degree in Environmental Science and another in Nuclear Engineering Technology, worked for government and industry for 20 years, and put enough scratch away to buy a research vessel. I travel all over the Caribbean providing a work platform to perform other peoples research. Next week may be 250 foot rebreather dive to support benthic characterization of one of the most productive fisheries in the Gulf of Mexico, the following week it may be studying shark populations in the Bahamas. This fall we are bidding a month long fish and benthic survey of Curacou and Montserrat.
I prefer to be on the periphery of the research. They can't do it without me or someone like me to haul them around, make sure their cylinders are full, and record their depth and bottom times for their respective universities. If I had it to do all over again, I would probably persue a degree in Marine Engineering with an emphasis on running ROVs, or AUVs, or doing exactly what I do, driving a small research vessel.
One thing to consider is joining the NOAA corps. I have a sometimes deckhand who just interviewed. She has a masters in Marine Biology but can't find a FTE anywhere, so she will give the Corps a try for 4 years and see if she can't break into a job somewhere.
Good luck to you. You are trying to get into something that a zillion of cute young hotties also do every year. Tough to compete with someone who looks great in a bikini, sorry to say.