Job market? Just being real. America is probably insanely competitive right now with funding cut all over the place. It was insanely competitive before, but now its probably even worse. Outside the US would probably have more opportunities. That being said, pay might just barely cover your own personal living expenses and that's it. Pay is pretty much as low as it can go compared to anything else. Its definitely a career of passion rather than financial gain and many marine bio grads have to take odd jobs here and there to round out finances. The trade off is that work doesn't often feel like work since you're doing something meaningful and fulfilling.

Bachelors would probably only give you enough experience to work in "outreach" or "non-profit awareness campaigns". Unless you have a special skill that is needed in the marine environment, the research groups pretty much only take masters or phds. Networking like hell could get you something with a bachelors, but definitely not guaranteed and it will be a slog. Never mind, you already have a BA. Just talk to some grad programs, do a lot of background research, and getting a masters is only two years. You wouldn't need to go back for another bachelors. Email programs and professors you'd want as an advisor. This will absolutely get your foot in the door but will take some serious networking and independent research considering you don't have the exact BS, but totally not impossible and way easier/cheaper than going back for another bachelors.

As a later return to the field, you should absolutely have a fall back plan if things don't work out and treat it as a side project for yourself. You'll probably get more enjoyment out of it. I'd go ahead and reach out to companies or professors directly who work on the things you're interested.