In Trouble on the St. Johns River, the Johnson kids Joey, Bobby and Katy are up to their adventurous ways again. But this time, instead of exploring history, they re making it! Joey and Bobby start their summer vacation by setting out for their favorite fishing pond, but end up leading a crusade to clean up the environment instead. Finding the pond covered with green muck and dead fish, the brothers decide to do something about it. That leads to a close encounter with a manatee, a visit to a center that rehabilitates injured sea turtles, and a boat tour on the St. Johns River.