By AMY HORTON

News Staff Writer

Two busloads of growth-minded city slickers rolled onto St. Simons Island Tuesday dragging a dozen prefabricated housing units in their wake.

Their goal wasn't to meet the luxury seaside living needs of butchers, bakers or candlestick makers. It was to provide underwater digs for sea trout, crabs, starfish and other critters.

The erstwhile builders came in the form of about 75 fifth graders enrolled at the Walker School in Marietta. Their science/community service project this year was to build "reef balls" for use at an existing artificial reef site off the Georgia coast.

If they work as intended, the reef balls will be a tremendous help for the coast, according to student Jeremy Walker.

Sounding as though his childhood enthusiasm for great inventions was battling the new-found skepticism of a scientist searching for a cure, Jeremy offered this explanation of the function of a reef ball: "They hope things that make reefs will attach on and make bigger reefs."

Reef balls are hollow concrete domes shot through with holes. When placed under water, they promote the formation of coral communities that attach to the surface of the ball and attract fish and other creatures in search of food and hiding places on the sea floor.

The individual units come in varying sizes, heights and thicknesses, and weigh anywhere from six to 90 pounds. Most of the weight is within one foot of the bottom outside edge, so they're less likely to shift with currents and the upheaval of storms.

A global organization called the Reef Ball Foundation provides grants for obtaining Reef Ball molds for anyone interested in creating units for new or existing artificial reefs. This is the first time they've been used in the construction of artificial reefs off the Georgia coast.

Walker School teacher Lorraine Brooks found out about the coalition from a friend and thought the project would provide valuable lessons for her students on many fronts.

"Every year, we look at something we can do with the class to teach civic and ecological responsibility," Ms. Brooks said. "This is not only important for nature and ecology, but I know it has an economic importance for people on the coast."

It took her students an intense two days to craft the reef ball contraptions out of concrete mixed in a wheelbarrow and poured into fiberglass forms provided by the coalition.

They boarded two buses at 6 a.m. to follow their creations to the coast. Once here, they boarded two boats and drifted into ringside seats to watch the Georgia Department of Natural Resources deploy the reef balls at an existing reef site in Jove Creek, just off the Intracoastal Waterway across from Troup Creek.

Such educational field trips to the coast are annual events for her students, Ms. Brooks said, and honors that all upcoming fifth graders dream of. Even after they've achieved the exalted status of high schoolers, students remember their magical trips to the coast.

"We look forward to this every year," she said. "This is an unbelievable place."