A great example of a horror film like Alien, The Thing, Sea of Devils and other films where an unknown monster methodically massacres a group of people in total isolation. Except that "The Creature from the Black Lagoon" was released before all of them, so it can be undoubtedly considered the ancestor of the genre, except for the earlier copies.
Not much can be said about the film. For those times it looks rather naive, especially since most of the things the main characters said about science, oceanology and space exploration have long since been revised and rethought.
However, the film is undeniably worth watching for all fans of the genre. There are not many special effects, and the characters play better than in many current horror flicks. Eh, they used to be able to shoot the real world masterpieces.