My PhD program is five years long, including course work and thesis research. I have always been attracted to biology because of the complicated ways which organisms find to solve problems of living in various environments. I started working on toxicology because of an interest in environmental sciences and how pollution we create in our society affects those organisms around us. I really enjoy working outdoors and near the water. The study of marine mammal toxicology has grown out of a fascination with environmental toxicology, whatever the species.
Marine biology is a vast field with many different types of research.
Working on marine mammals can be difficult due to the number of people interested in them. The key is to find a good school with a wide variety of marine courses to find out what you like. Most marine biologists probably work on plankton or fish because these are the organisms which are of greatest abundance in the ocean. It takes a lot of time to become a scientist but there are lots of jobs that do not require a PhD and that level of training. I think the key is to find out what basic subject area you like- toxicology, behaviour, physiology, ecology, evolution, development and then go from there.