There’s a lot of mysterious creatures and rare species hidden in the dark depth of the sea. One good example is the sea slugs, with more than 3,000 different species of them. Most of these sea slugs are snails that lost their shells, and gained new features through their complex evolution. Sea slugs draw lots of attention because of their amazing colors and shapes, and they sure do make life under the sea way more interesting and beautiful. Here is a special selection of weird yet stunning sea slugs that will definitely make you believe in aliens. Enjoy!