On a Research Ship
A marine biologist could be working aboard a research ship for 1 to 2 months. The ship usually runs throughout the night, as it can be easier to catch and release animals for research at night. Additionally, while a biologist will primarily spend time doing research, if there are repairs needed on the boat, that will take precedence. Once a biologist gets up, he will usually get straight to work. That work will customarily involve deploying nets to get samples. Once the biologist has samples, she will study them under a microscope and take notes. The next day, the biologist will usually take another sample in a different location.
At a Coastal Field Station
A biologist based at a coastal research station may often work with other scientists and undergraduate students who assist with the research. A biologist may begin his day by organizing tasks for everyone, preparing equipment and donning gear (like scuba gear) to collect samples. Once those samples are collected, the biologist will organize them, placing them in tanks to take them back to the lab for later research. The marine biologist then returns to the lab to conducts data analysis and experiments on the samples. He may also tag and release samples.
Teaching at a University
Marine biologists who teach at universities will typically divide their time between conducting their own research at the school and teaching students. While doing research at a university, a biologist is expected to publish papers in journals reviewed by her peers, as well as to review papers by fellow marine biologists. In addition to giving lectures, biologists are also expected to supervise research students who are pursuing their masters or Ph.D. In addition to the research papers and teaching duties, a marine biologist at a university may spend her days in committee meetings with fellows in her department, and applying for research money.
At an Aquarium
Working at an aquarium requires slightly different skills on the part of a marine biologist than simple research. Here, the biologist will spend a good portion of his day working with the public.This could mean giving a talk to schoolchildren or college students, or even talking to the general public about a particular display at the aquarium. In addition to talking to the public, a marine biologist at an aquarium will spend a good part of the day taking care of the animals. This involves donning scuba gear to clean a tank and feeding and monitoring the animal's health.