Acoustic system protecting manatees

A simple sound wave, silent to most ears and beamed underwater, may save the languorous manatee from being crushed to death in Florida's massive boat lock gates, which can stretch 54 feet wide and weigh up to 40 tons. When a manatee blocks the acoustic beams, which they cannot hear, the gates stop and remain open long enough to allow them to pass through safely.
- I'm hoping this is the culmination of science and engineering that can be used to begin creating manatee-safe structures," says Patrick Rose, executive director of the Maitland-based Save the Manatee Club.
Since 1975, 191 manatees have been crushed or drowned in boat locks or flood gates. They are protected under the federal Endangered Species Act.