Flush, by Carl Hiassen, 2005

When Noah's dad gets into trouble, as he frequently does, he tends to go a bit overboard, even if his heart is in the right place. This time he sunk Dusty Muleman's casino boat, the "Coral Queen," for dumping its sewage into the ocean. But the Coast Guard has no proof, and Noah's mom's had it with her husband's antics. Noah and his sister Abby have more to save than loggerhead turtles -- their home and livelihood's at stake if they don't find a way to bust Dusty's foul-smelling operation. Environmentally conscious middle-grade fiction, lyrical Florida Keys setting, villians, and humor. Recommended.