If you've been to a beach in your lifetime (and who hasn't), you've probably spent some time searching for shells. Shells are grown by animals that live in the ocean, who use them as a hard layer of protection against predators. After they die, other animals eat away at their bodies and all that remains is the shell.

There are many types of shells that grow on animals under the sea, including mollusk, clam, chiton, snail and tusk shells. Most shells found on beaches are from marine mollusks and this is partially because their shells are made of a more durable calcium carbonate. Mollusks date back over 500 million years and there are over 100,000 different known species. Against popular belief, not all mollusks are found in salt water, as some live in fresh water as well as on land.

For thousands of years, humans have used shells for a multitude of different purposes and continue to rely on them to study evolution. Today, many enthusiasts have shown their love for shells through tattoos and we've curated some of our favorites of the bunch. Take a peek at 75 sensational sea shell tattoos in the gallery below, then let us know your thoughts on these tattoos in the comments section on social media.