I studied biology, took special classes in marine biology, and now I am in a Psychology graduate program. I was interested in dolphins and whales when I was in high school, and that originally directed me to study them as a career. But what I realized later is that the study of any animal or system of life is a study of many fields of research - biology, genetics, math, physics, psychology, ecology, oceanography, etc. I could say I would work at my computer less and be outside more, but I do like working on my data, looking at the echolocation clicks our dolphins make. Researchers need funding to do their work and unless there is unqualified understanding by everyone that we do need to learn about other species' lives in order to understand our world better, its makes it very hard to get research done.
Marine biologists make less money, that's a con.
But we get to study and learn more about some of the most beautiful animals on earth, that's a pro. It is hard work, but it can be very rewarding at times. I also organize a metting group for marine mammal students in Hawaii, and, of course, I have my life outside of my professional career. We would know very little about the incredibly diverse life that exists under the surface of the ocean. Indeed, as we humans begin to turn to the ocean more for means to our future survival on Earth, we need to know how our actions might impact that ecosystem.