I definitely remember watching this when I was about five or six years old. We were living in a trailer at the time and I recall they sold special 3-D glasses so the TV show could be seen the way it was intended.
The Creature from the Black Lagoon follows the exploits of Dr. David Reed, whose friendship with another scientist pulls him into the orbit of the Creature. Dr. Carl Maia discovers the fossil of a webbed hand that would link amphibians to humans. As he returns to the states to tell his friend and his boss, the Creature attacks and kills Maia's assistants who were left behind. The gang all return and decide to explore a region from which no one emerges known as the Black Lagoon. While they explore, they run afoul of the creature, who has the hots for David Reed's girlfriend. Hilarity ensues as the gang takes on the Creature.
This is really a B-movie at best and I think it gets lumped in with other classic horror so much because of the design of the Gill Man. The Creature was pretty original at the time and looks slickly terrifying. The action isn't all that exciting and the lumbering nature of the creature means it is in the same class as men in gorilla suits. I remember the creature getting stuck in the trawling net of the boat and losing a claw, this might be the origin of my fingernail queasiness. The underwater scenes are something to see, of course.
I can't say this is a frightening movie but it is good for a few thrills.