If aliens landed on our planet tomorrow, capable of breathing in any condition, they’d likely find the depths of our oceans the most intriguing and relatable aspects of this planet. As land dwellers, however, we’ve only begun to explore the depths of the underwater world.

In the spirit of summer and thoughts of the sea, we went on an internal expedition for images of the underwater world (we think) we know of, in search of the most intriguing creatures and deep-sea visions. Below, you’ll find some of our most beautiful and unique picks, paired with random facts — because the water is teeming with them.

1. The Sea Urchin

Image by Joze Maucec

These fascinating “underwater hedgehogs” are able to move around via tiny tubes that function as their feet. Hydraulic pressure and a water vascular system work in conjunction to pump water in and out of those tubes — hence, mobility!

2. The Sea Slug

Image by CK Ma

These colorful sea-floor dwellers emit sounds that are audible by humans. According to one professor, they sound like a steel wire hitting the side of a glass jar. We can only assume that these sounds are made in an effort to communicate or fend off predators.

Pictured: [1] Image by CK Ma [2] Image by CK Ma

3. The Frogfish

Image by CK Ma

Like most sea dwellers with elaborate coloring and structure, the Frogfish’s physical appearance can not only adjust to its surroundings, but functions as a way to ward off predators and attract prey.

4. The Black Jack

Image by DJ Mattaar

Typically seen traveling as a group or “school,” these fish tend to be predatory in nature and can usually be found in the offshore regions of tropical zones. They possess black grey fins and jet-black scutes.

Pictured: [1] Image by CK Ma [2] Image by CK Ma

5. The Red Cushion Sea Star

Image by Peter Leahy

You’ve probably heard of this little guy — but did you know that the Oreaster reticulatus actually eats from the floor of the sea by gathering heaps of sediment? It then proceeds to turn its centrally located stomach inside out and engulfs the sediment.

6. The Nautilus

Image by Taras Chykhman

This extinct mollusk is considered to be a living fossil, having rarely evolved or changed over the course of millions of years. They swam with jet propulsion by drawing water in and out of their living chamber. They were assumed to lack intelligence, but recent experiments suggest that there might have certain memory and response traits.

Pictured: [1] Image by bluehand [2] Image by bluehand

7. The Red Big Eye Snapper

Image by aquapix

Pricanthidae can be found in deeper waters, usually reachable by scuba diving. Their large eyes assist with their carnivorous and nocturnal existence. The earliest fossils of these fish date back to nearly 40 to 50 million years ago.

8. The Cleaner Shrimp

Image by iliuta goean

These tiny critters exist in a world where their livelihood is beneficial to not only those they feed off, but also themselves. By living off the parasites and other things that infest fish, the shrimp get nutrition, while the fish they eat from get a free cleaning.

Pictured: [1] Image by Olin Feuerbacher [2] Image by iliuta goean

9. The Bluespotted Stingray

Image by Hendrik Martens

This species of stingray is a predator to mollusks and many types of fish, but is also sought after by Killer Whales and Hammer Head Sharks. Their bright yellow eyes are positioned so that they have a wide-angle view, and their mouths don’t have teeth, but rather food-crushing plates on the sides.

Top image by Marquicio Pagola

For more deep-sea exploration, check out our full Underwater Oddities lightbox »