Tentacles, flippers, and fins—the world beneath the sea is filled with life that looks like something from an alien planet! It's a wonder that we can know so little about some of the very animals that share this Earth with us. Researchers like Jacques Cousteau spent their lives trying to unlock the mysteries of the deep, after all. And it's only because of the hard work of sailors, marine biologists, and deep-sea divers that we know as much as we do about those animals. Well, we mixed our fascination with life under the sea and our extensive knowledge of costuming to create a great selection of costumes based on your favorite underwater critters.

Of course, it can be a little challenging to make a choice with such a wide selection! Do you want to dress up like an enigmatic squid from the depths or a cute narwhal cruising the coast? Maybe you want to be an apex predator of the seas and wear one of our many shark costumes. Well, we want to help you make your choice! This guide will help you weigh your options and choose the right sea creature costume for you.

Let's start with sharks. Sharks are known as some of the fiercest predators in the ocean. Thanks to Jaws and Finding Nemo and the ever-popular Shark Week, everyone knows the awesome power of sharks! Aside from being incredible hunters, many of them have some unique features to distinguish them from other fish in the sea. These sleek critters' scales are more like tooth-shaped spines. Some of the more iconic sharks—like great white sharks—also need to keep moving to make sure enough water flows through their gills. If you're looking to unleash your inner ferocity on the ocean or on the next costume party, then dressing up in one of our shark costumes is a perfect choice.

And then, there's the lobster. Far from being an apex predator, these crusty crustaceans crawl around on the ground, looking for anything it can munch on. Lobsters don't get quite the love that other critters do, but we think they deserve a little more attention. Did you know that lobsters don't age? It's true! Their genetic material doesn't deteriorate like most animals, so even though a lobster gets older and larger, it doesn't get "old" as humans do. Of course, they end up having another problem after living for many years. They get too big! Lobsters need to molt as they get bigger, but that takes a TON of energy. So if they reach a ripe old age, they can just get too exhausted while attempting to molt and meet their end!

Yep, lobsters are a strange and cool creature. If you're a strange and cool human, then you might want to dress up like one. We carry some lobster costume options that will have you scuttling across the ocean floor. Oh, and no molting necessary to slip into any of these.

Ever feel like you don't have enough arms? It's kind of an odd question, but it's something we think about way too much—mostly when we're trying to carry groceries inside. Instead of taking a dozen trips, we could just carry all of the bags in at once. Well, that's a problem the octopus doesn't have. Not only because octopuses don't buy groceries, but also because those curious cephalopods have 8 arms, kind of like the spider of the ocean. If you dream of having some extra arms, then it's time for one of our octopus costumes.

The oceans are a big place! They take up over 70% of the Earth's surface, and not every animal living in the water is strange and creepy. Let's change gears to one of the sea's most adorable creatures, the narwhal. The narwhal looks sort of like a magical animal that would be the main character in a fantasy story. Its sleek look and single horn give it a unique appearance! So if you want to feel like the unicorn of the ocean, then one of our narwhal costumes is going to be the perfect choice for you. Check out some of our favorite options below.

Ever since we watched The Hitchhiker's Guide to the Galaxy, we've always had this sneaking suspicion that dolphins might be smarter than us! It's definitely true that dolphins are the brainiacs (not to be confused with the Brainiac of Superman comics) of the sea, and if you want a smart sea creature costume, then our dolphin costumes are exactly what you've been looking for.

We've covered a lot of animals on our list, but we didn't stop there. Our costume designers are dedicated to crafting costumes for everyone, and that's precisely why we have such a large selection of Made By Us exclusives. Many of them are niche outfits, and they're ones you won't find anywhere else. They studied all sorts of different underwater environments to get these sea creature costumes for adults to look just right! If you want something that's a little out of the ordinary, then try just take a look at some of our specialty costumes below—you might just discover the perfect catch!