For six days, a small group of college students worked aboard a high-tech marine research ship as it has cruised western Long Island Sound on a scientific excursion meant to learn more about that vast body of water. They have made at least one interesting discovering: sediment 66 feet below the water's surface, evidence of a river that existed more than 10,000 years ago.

Their work is still in its preliminary stages, but the group, mostly upperclassman pursuing majors in different scientific fields, hope to flesh out the Sound's early history and its current health after taking the material back to their college labs for further analysis.

''It's the kind of stuff that we read last semester in textbooks, and now we're doing research on it that might get published,'' said Naisa Thacker, 21 a Queens College junior majoring in environmental science. ''It's very cool to be a part of it.''

While the research is important, the journey, which ended yesterday, had a bigger goal. It is part of a national effort meant to increase the representation of minorities in certain science careers. All nine students on Long Island Sound are minority students at City, Queens and Lehman Colleges, and their trip was financed primarily by a National Science Foundation grant to address the underrepresentation of minorities in the earth sciences.

In 2003, of 14,655 graduate students studying earth, atmospheric or marine sciences, 375 were Asian or Pacific Islander, 270 were black, 484 were Hispanic and 66 were American Indian or Native Alaskan, according to the most recent foundation statistics.

''We realized that we haven't done a good job of recruiting the underrepresented groups in the geosciences,'' said Rhonda Spidell, who works on diversity and education issues related to earth sciences for the foundation. Ms. Spidell said that other fields, particularly biology, tend to have greater appeal, ''but in geoscience we have a very important science that informs the citizenry of what's going on in the planet.''

''I think that it's just been overlooked,'' she said.

The students boarded the Hugh R. Sharp, a 146-foot research vessel owned by the University of Delaware, at a dock at the Maritime College of the State University of New York, in the Throgs Neck section of the Bronx, on their mission to measure the topography of the seafloor and to study the effects of pollution on marine life, among other things.

Aside from identifying evidence of a long-vanished river, the student researchers have also found thin-layered sediments 115 feet below the seafloor that indicate the existence of a lake before advancing glaciers deepened the Sound's waters to more than 100 feet.

''The Long Island Sound has a unique geological history,'' said Alexandrea Bowman, 29, a Queens College student who is majoring in geology and English. ''I've been looking at some of the mud that's been coming out of the cores, and so far we've found some very different seafloor environments in near areas.''

By Sunday, the students' initial excitement had turned into frustration. They were not familiar with the advanced research equipment, including a chirp sub-bottom profiler, which uses sound to penetrate the seafloor and provide a picture of its cakelike layers. But each day, their skills improved, and over the next few days the group collected 19 sediment samples and mapped the topography of the seafloor.

''It's actually becoming pretty draining,'' Wanda Vargas, 36, said on Day 5. ''You get into a routine where everything has to be so precise. It's much more of a mental challenge.''

Cecilia McHugh, a professor of marine geology at Queens College who helped secure the National Science Foundation grant and guided students as they conducted their ship-based research, uses her own story in an effort to inspire minority college students to consider marine science as a career. Professor McHugh came to the United States from Argentina in the early 1970's knowing no English and married and raised two sons before attending night school and eventually completing her doctorate in marine biology.

''They're coming from backgrounds that don't have much means, and science, mathematics, physics are scary things,'' she said of the students she has taught. ''They think they cannot do it, and it's not true. They're all very capable.''

One of the students on the research ship, Arthur Cortes, a senior at Lehman, said weekend fishing trips to Orchard Beach ignited his desire to study marine biology. After returning to the mainland, he said six days was not enough. ''I want another six months on it,'' he said.

Photos: Top, the Hugh R. Sharp, a 146-foot vessel owned by the University of Delaware, pulling away last Friday at the start of the trip. Above, Lily Leon of Queens College prepares equipment used in the students' research. (Photographs by Richard Perry/The New York Times)