sentence: the most famous include how the '' bottom '' of the lake is a false bottom made up of silt , under which lies a spring that extends feet below the surface of the lake ; that somewhere in the lake lies a crashed airplane ( either a b-17 flying fortress or a small private airplane , depending on who you talk to ) ; and that scuba divers reportedly dove the deepest depths of the lake only to surface when the fish became larger than the divers .