As part of the Three Seas program at Northeastern University, student Stephanie June partook in a diving expedition to examine coral reefs off the coast of Panama.

But her fondest memory of the underwater excursion had nothing to do with exploring the so-called “rainforests of the sea.”

That’s because midway through her deep-water dive, she experienced a once-in-a-lifetime encounter with a harmless 30-foot-long spotted whale shark.

Of meeting the largest living fish species on the planet, the senior biology major says, “Out of nowhere, this shark was right underneath me. Very rarely do you get to see them.”

Now in its 28th year, the Three Seas program enables students to study and conduct research in three diverse environments with many of the world’s leading marine scientists.

Run by the Marine Science Center (MSC) at Northeastern University, graduate and undergraduate students spend the fall semester at the MSC in Nahant, Mass. The only major, year-round marine laboratory in the Greater Boston area is just 12 miles from campus and has classrooms less than 100 yards from the Atlantic shorefront.

In the winter, students study at the Smithsonian Tropical Research Institute in Panama for three months, followed by a two-month stint in the spring on San Juan Island, Wash.

The program — which includes daily lectures, fieldwork and diving expeditions — is taught by marine biologists from leading research institutions, including Northeastern University, Brown University, Scripps Institute of Oceanography, and University of California campuses at Berkeley, Santa Barbara and Santa Cruz.

Senior biology major Sonia Ahrabi-Nejad praises the experiential learning opportunities at the core of the program. “By being out there for an entire year, in three different labs, with top research professors, I feel more prepared for grad school and a career than if I was just sitting in a classroom,” she says.

“You’re not just going out and enjoying the Caribbean for two months,” June adds. “You have to work hard.”

This fall, Northeastern expanded the marine biology concentration to a marine biology major in the College of Science.

Sal Genovese, director of the Three Seas Program, compared training students in the new discipline to preparing minor league ball players for the big leagues. “Through the new major, we can home grow our own marine biologists,” he says.