The Sea Monster is an aquatic creature in the Goosebumps book Deep Trouble.
History
Billy Deep ran into the sea monster while snorkeling. He tells his sister Sheena what he saw, but she didn't believe him.
At the end of the story, Billy runs into the monster again while looking for The Mermaid.
Appearance
It is a huge dark green monster with one brown eye, twelve octopus-like tentacles, and has two rows of sharp teeth.
Concept Art
Goosebumps Movie's Sea Monster Concept Art
The Sea Monster was originally going to appear in the Goosebumps Movie due to appearing in concept art, but it was replaced by E. Ville Creeper's Plants from You're Plant Food!. In the concept art, he has a dark green tone, four red eyes, no-visible mouth, and eight octopus-like tentacles.