Director Barry Levinson was approached to do a documentary about the Chesapeake bay. He watched another documentey about the Chesapeake bay that talked about the pollution and the lack of fish. He said it was a great documentary but nobody will care about it. And so he said he would take all of the facts about the Chesapeake bay and turn it into a theatrical base piece.
The parasitic crustacean depicted in the film is Cymothoa exigua (Schiødte & Meinert, 1884), as known as tongue-eating louse. The female parasites fishes by attaching itself to their tongue where extracts the fish blood causing the thong to atrophy. The parasite then replaces the fish's tongue and feeds on the host's blood or mucus. That explains why many townspeople are found with their tongues extracted.