The scene of the alligator stalking past the sewer tunnel supports and the shot of saliva under a microscope were both stock footage from the original Alligator - O Jacaré Gigante (1980).
The shot of the alligator opening its left eye after hearing the hunters in the sewer and the overhead shot as it enters the water to attack Vincent Brown were both stock footage from the original Alligator - O Jacaré Gigante (1980).
Billy Boy is played by stuntman actor Kane Hodder. Hodder was uncredited as the alligator in the first Alligator - O Jacaré Gigante (1980).
Buckley Norris (Doc) also starred in the original Alligator - O Jacaré Gigante (1980) as a character named Bob. He is the only actor, aside from Kane Hodder, to appear in both films.