Manatees, aquatic mammals inhabiting Florida' s rivers and coastal waters, swim close to the surface and are frequently killed in collisions with boats  To address the problem, boat traffic in manatee-populated waters is being required to maintain very low speeds  Unfortunately, manatees are unable to hear low-pitched sounds and a boat' s sound lowers in pitch as the boat slows
Ttherefore, this approach may in fact make things worse rather than better
Over the last several decades, boat traffic in Florida's coastal waters has been increasing almost continuously and now represents the greatest threat to the endangered manatee population.