When I was a kid, I saw a movie at our local library about a lake creature, possibly a dinosaur, that was trapped on one side of a dam. The creature would follow the lights of the boats at night. A teenaged boy figures out the creature is trying to get to the other side of the dam and helps it get there.
After the creature gets to the other side of the dam, we find out it’s mate was on that side.
I remember one another scene in the movie. The boy finds a cave with water in it. On the wall of the cave, he finds the fossilized head of one of the creatures.
What I am calling a creature, looked like a dinosaur. It had four flippers, a dinosaur looking head and a short neck. It was like the Loch Ness monster, except it’s neck was much shorter.
I would have watched this movie in the 1980s or early 1990s. It was in color and in English.
Thanks for your help!