Much more common in manmade lakes - at least as infectious organism. The Amoeba, I mean. Apparently from the large amounts of stuff drowned and decomposing. Which includes, in the case of manmade lakes, an unusual concentration of drowned mammals. Brain cells, other dead wood - maybe it's a specialist. There's no official word on whether it gets its start on its new food source from human bodies - mob hits, drunken fishermen, political enemies of casino developers. I know that one! It's the talking bomb from Dark Star. I don't usually get lines from movies.