782 manatees are known to have died so far this year, far outpacing the 637 all of last year. reporter: the problem beneath the surface is the sea grass the manatees eat is disappearing. they re literally starving. it s depressing. reporter: scientists like grant gilmore blame pollution. that is what we think is the primary issue right now is because we know we ve documented this disappearance of sea gas. reporter: he says runoff from industrial agriculture and florida s booming urban devlopment dumps chemicals into waterways that empty into these estuaries. the in balance causes naturally occurring algae to float blocking sun light and killing the sea grass. and it s not just affecting manatees, correct? no, it s affecting all of the fish, the crabs, everything that is dependent on the water out here and sea grass. reporter: left unchecked, this could also impact florida s fishing and tourism industry. barry legge hopes people tart start to pay attention if only for the