There is a thread in the photography forum on inverts by Shoreliner and that has some current discussion. And there was another recent thread on it as well. https://www.saltwaterfish.com/vb/show...rine+biologist
Unfortunately, it is a HUGE field of study so it is difficult to give general details. It can refer to all manner of types of work. There is no one "job" that a marine biologist does except to say that it deals in some form with life in the ocean, or with other environments impacted by the ocean.
Got a B.S. in biology and a M.S. in aquatic biology. Did my thesis on an impact study (benthic marcoinvertebrates, water chemistry, and fish surveys). Glad I got my MS, but wouldn't want to do it over again.