When Dorian Cabanit was touring the North Shore for a class project, he was struck by how brown the water was.

"From the map, it doesn't look that dirty, but you can see how it is in person," said the Damien Memorial School eighth-grader. "It just looks like a Yoo-Hoo."

His classmate Nick Sakamoto is concerned about the dirty water washing into the Ala Wai Canal. "There's all different kinds of rubbish and old fishing nets," he said. "All the pollution and run-off is very bad."

The boys have created two of the four models Damien science students are entering in Saturday's Model Watershed Contest sponsored by Protect the Planet.

Marcus Finau, who worked on the same model as Nick, said they were including dead fish on their model. "You can't eat the fish in the water because it's so polluted," he said.

However, the model also will include the fishermen who catch and eat the fish despite the dangers of contamination.

This is the second time science teacher Georgia Nguepdjo has had her students enter the contest, although this is the first time since she started teaching at the Catholic boys school in Kalihi last year.

Nguepdjo, a former Peace Corps volunteer and community development worker, has a strong background in environmental issues, particularly in fisheries and agriculture.

Nonpoint-source pollution is an important issue for science classes to tackle. "I think it's kind of a hot topic right now," she said. People who live in O'ahu's valleys need to consider what's ending up in the water when they wash their cars or put things down storm drains, she pointed out.

The boys entering the contest are doing so on top of their regular physical science work and the beginning preparations for their science fair projects. Although the boys say they're doing it to boost their science grades and vie for a $100 prize, she notes that none of them is behind in science.

"I really applaud my guys," she said. "You can't be slow and do three things at one time."

The projects have taken about a month to prepare and required the students to give up some lunch breaks and weekends.

Nathan Tehada, a 15-year-old freshman, explained that the models are built on a platform, with a model sealant foam to build the landscape. The boys did Internet research on their various watersheds and built the models according to maps they found through Google.

Wayne Segundo, a 13-year-old eighth-grader, included Kuhio Park Terrace, Kamehameha IV housing, Kalihi Waena Elementary School and Nimitz Highway in a model that includes Kalihi Stream. His model also shows "all the pollution and stuff we have in the stream, the batteries, and tires and rocks."

His classmate and partner Nephi Tuitele, also 13, notes that their model ends with sand to represent Ke'ehi Lagoon, where the polluted water ends up. "It just opens up into the ocean and harbors," he said.

Noah Puaala-Ortiz, who worked with Dorian on the Kaiaka Bay model, said they painted all their water brown to represent the agricultural run-off in rural Hale'iwa.

Nathan, whose model showed Kane'ohe Bay, wants people to learn from his project "that nonpoint source pollution can come from all sources."

Reach Treena Shapiro at tshapiro@honoluluadvertiser.com.