That whole “hold a shell up to your ear and hear the ocean” thing is a hoax that was started by the brain crabs. They are very tiny parasites that hide out in abandoned shells waiting for a host to pick it up. The enter through the ear canal and latch on to the brain stem. The are mostly harmless but can influence you in subtle ways like getting to to tell others that you can hear the ocean when you hold a shell up to your ear. Back in the 1950’s someone held a shell up to a horse as a joke and inadvertently created Mr. Ed.