reporter: it is estimated there is only 6,000 manatees left in florida. they survive on sea grasses. a single manatees can eat as much as 300 pounds of it a day but for more than 80 miles along the east coast, the bottom has become a dessert like trees in a forest, the sea grasses need sunlight to grow. but pollution from waste water, leaking septic tanks and fertilizer from yards and farms have washed into the coastal waters of florida. those nutrients cause algae to grow. it s so thick sunlight can t penetrate to the seabed and without sunlight, sea grasses do not grow. we re talking being down 900 pound to three-quarters of your body weight gone. they re skeletons. reporter: in a first ever, florida wildlife biologists have tried to feed manatees but so far the lettuce that they love to eat with gusto when they re in a manatee recovery pool like this has not happened in the wild. at this point, the animals aren t