Hiaasen, Carl. Double whammy. New York: Warner Books, 2003 (originally published in 1987). ISBN 0-446-35276-4.

Summary: A hypercompetitive bass fisherman hires a private investigator to prove that one of his rivals in leading bass fishing tournaments has been cheating -- catching bass in advance and imprisoning them in underwater cages until tournament day. With the assistance of several locals, ranging from the fearless to the demented, the private investigator manages to break the case, which turns out to be both twisted and dangerous.