"Shell Shocker" was the eighth short story featured in the book More Tales to Give You Goosebumps.
Tara and Tommy are arguing about who has rightful claim to a beautiful seashell found washed ashore at the beach. Tommy only wants it so that he can listen to the ocean through it, despite Tara knowing you really can't hear the ocean inside of a sea shell. She mocks her brother, while explaining her own reasons for wanting such a beautiful shell as her own.
She then goes on to try to think of possible ways she could win ownership of the shell, or trick her brother so that he will give it to her. She then has to go to school and brings the shell with her. She then wins the shell, eventually. and begins to humor her brother.
Soon enough, she is beginning to hear voices inside of the shell. Crying out to be saved. She believes the voice and follows it to the directions that lead to a mysterious cave out of the way where she is promised the biggest sea shell in the world if she helps the being trapped in the smaller shell. Eventually, it turns out Tara was tricked!
She travels very deeply into the cave, to come across the biggest shell, as promised. However, inside the shell is a huge hermit crab! It grabs Tara in its claws as the little voice from within the smaller shell suddenly cries out to his mother, saying that it has tricked another victim.