Students should attend graduate programs that specialize in their area of interest. You will need to research the programs first to see if they are right for you. Many Websites, such as those listed below, offer descriptions of graduate programs:
GradSchools.com - This site lists descriptions of graduate programs in the environmental and natural resource economics field that are available throughout the world.
The Chronicle of Higher Education - You can find rankings of the various U.S. departments specializing in the field on this site.
For marine affairs, there are many related programs at numerous schools. However, one of the best is right here at the University of Rhode Island, where you can earn a Master, Master of Arts, or Ph.D. in marine affairs. See the department Website for more information: http://cels.uri.edu/maf/Default.aspx.
Another great way to learn about the opportunities available in graduate school is brainstorming with friends or colleagues who already have graduate degrees or who are currently attending graduate school. You can search online for individual programs near where you live or in areas where you would like to live. Your undergraduate program faculty and advisor are great sources of information regarding graduate programs and graduate study in general.
Prior to sending out applications (which costs you time and money), it is a good idea to visit potential programs to meet faculty and graduate students and to get a sense of "fit" for your specific interests and needs. If you are unable to physically visit campus, ask a faculty member for contact information of current students so you can talk to them and ask questions. It is common for current marine affairs graduate students to get contacted by prospective graduate students with questions about the program and student life.