Well seeing as text books are typically made for colleges and universities there is a limit to the amount of text books published and reprinted each year because the only people who will be buying those books are college students. So this results in a insane price tag on almost all text books unless you buy old editions or ones that have been worn out.
Best advice to find text books on marine biology is go to Amazon and on the left click the books category and select textbooks. then search "Marine Biology" and you'll get tons of results, just did it and there's some cool stuff there but pretty pricey.
BTW you mean textbooks right? And not just books in general?
(please tell me this didn't brake any rules!?!?!?)
Well, been out of it awhile and haven't seen recent texts.
Castro and Huber (Marine Biology) is a popular one.
Also a pretty new one called Introduction to Marine Biology by Karleskint, Turner, and Small. Richard Turner was a mentor to me.