Enemy Unseen (1989)

A couple of young scientists, Mel Noble and Roxeanne Tangent, travel to an island in Africa thought to be deserted in search of crocodile life, when African Natives storm the camp and kidnap Roxeanne. Her father, Gordon hires Steiger and his team of investigators to track down the natives that worship crocodiles as sacred animals. The problem is: they can't be seen. With natives in the jungles and crocodiles in the waters, Steiger and his crew must fight to survive and save Roxeanne from being sacrificed in a gruesome ritual with an "Enemy Unseen". —spyguy88