1. Sawfish
   Gudgeon fish
2. Greenland shark
   Mako shark

The bizarre Greenland shark is known for being extremely slow-moving and extremely old. Their lifespan is between 300 and 500 years, while their top swim speed is around 1.6 miles per hour, which has actually confused scientists who aren't sure how they can even hunt prey.

1. Lobster
   Mollusk
2. Crawfish
   Violet sea snail

While lobster is considered quite a luxurious food item today, that wasn't always the case. Once upon a time, lobster was considered a bottom-feeding sea bug and only suitable as food for peasants and the lower class.

1. Mackerel
   Mahi mahi
2. Sea bass
   Yellowfin tuna

Yellowfin tuna is much larger than many people realize, with specimens getting up to around 400 pounds in size. That sounds enormous, but it's still nowhere near as big as some tuna-like bluefin, which can reach nearly 1,000 pounds.

1. Porpoise
   Nurse shark
2. Dolphin
   Narwhal

There are over three dozen species of dolphins in the world, from river dolphins to bottlenose dolphins. Even killer whales, which are obviously referred to as whales, are actually a kind of dolphin, genetically speaking.

1. Barnacles
   Geoduck
2. Giant clam
   Zebra mussels

The largest giant clam ever found dates back to 1817. The clam was no longer alive, but it weighed 510 pounds and probably would have been 550 lbs when it was still alive. The shell was 4'6" across.

1. Sea cucumber
   Cuttlefish
2. Nautilus
   Blue-ringed octopus

Blue-ringed octopuses are relatively small, but should never be underestimated as they're one of the most deadly animals in the sea. One octopus has enough venom to kill 26 adult humans in a matter of minutes.

1. Moray eel
   Olive sea snake
2. Blue krait
   Oarfish

Moray eels are generally found in saltwater, but a few kinds can live in freshwater as well. They have what is known as a pharyngeal jaw, which is a second set of jaws, with teeth, in the back of their mouths.

1. Sawfish
   Hammerhead shark
2. Cuttlefish
   Mako shark

Hammerhead sharks tend to spend most of their time in warm waters but will migrate to cool water in the summer. Compared to most other shark species, they have oddly small mouths. Despite that, they can also be aggressive towards humans.

1. Right whale
   Sei whale
2. Narwhal
   Blue whale

Blue whales are larger than any animal in the world, living or extinct. They grow to the impossibly massive size of 98 feet in length and weigh around 190 tons. That's about the size of 95 Ford F-150 trucks.

1. Stingray
   Pufferfish
2. Conger eel
   Sea krait

Stingrays are usually not confrontational and rarely attack humans. Steve Irwin, the Crocodile Hunter, tragically died after being pierced by a stingray's barb, but it was a very rare accident and only the second death from one of these fish since 1945.

1. Viper fish
   Vampire squid
2. Angler fish
   Lion's mane jellyfish

The vampire squid looks like a bit of a floating nightmare, but lucky for us, it lives at extreme depths and is only about 1 foot long. The scientific name for these animals is "Vampyroteuthis infernalis," which literally means "vampire squid from Hell."

1. Rock lobster
   Lionfish
2. Yeti crab
   Giant prawn

The yeti crab, sometimes called a yeti lobster for its furry-looking appendages, is a relatively newly discovered species, having first been officially identified in 2005. They're deep-sea creatures that live near hydrothermal vents.

1. Pufferfish
   Box jellyfish
2. Cuttlefish
   Nautilus

There are actually several species of box jellyfish, and not all of them are equally venomous. That said, they get their deadly reputation from the fact that some people have died after envenomation in as little as two minutes. Shown here is Chironex fleckeri, one of the deadliest of the box jellyfish.

1. Walrus
   Narwhal
2. Puffin
   Manatee

Walruses are some of the largest non-whale mammals you'll find in the sea. Over the years, hunting has drastically reduced the walrus population in the world though they have been rebounding slightly in the last few years.

1. Wolverine
   Kodiak bear
2. Kingfisher
   Polar bear

Found exclusively in the Arctic regions of the world, polar bears spend so much time in the water they're often classified as marine mammals like walruses and seals. Bears have been recorded swimming for as long as 10 days at a time at distances up to 220 miles.

1. Sea bass
   John Dory
2. Pufferfish
   Mahi-mahi

Pufferfish are some of the most famous fish in the world, not just for their ability to puff up like a balloon to defend themselves, but also because of their toxin. The meat can be eaten, but if the toxin found in many of their organs and skin gets into the meat, eating it can be fatal.

1. Spindle crab
   Rock lobster
2. Crawfish
   Mantis shrimp

Mantis shrimp are amazing little creatures. Not only can they attack with blinding speed and power, but they also have incredible eyesight that a human couldn't even begin to understand. We have three photoreceptors in our eyes while mantis shrimp have 12 to 16 and can see a range of wavelengths from ultraviolet to infrared and beyond.

1. Walrus
   Manatee
2. Porpoise
   Harbor seal

Manatees are slow-moving, herbivorous mammals. There's a popular belief that early stories of mermaids told by sailors hundreds of years ago were actually inspired by manatees swimming alongside the ships.

1. Sea slug
   Abalone
2. Plankton
   Tube worm

Sea slugs come in all kinds of shapes and sizes and are actually gastropods, which makes them more properly snails without shells rather than slugs. They can come in a wide variety of colors as well, including bright blues, greens and reds.

1. Salmon
   Rock cod
2. Bluefin tuna
   Rainbow trout

You can find salmon in all sorts of rivers across North America and also in the Atlantic ocean, the Pacific Ocean and as far north as the Arctic as well. Most species spawn in freshwater before making their way back to the ocean.

1. Sardine
   Mackerel
2. Trout
   Flounder

Flounders are flat like pancakes, and as a result, they're most often found on the seafloor. Overfishing has taken a brutal toll on flounder populations. It's estimated the population is one-tenth of what it was at pre-industrial levels.

1. Geoduck
   Zebra mussels
2. Abalone
   Razor clam

Abalone is a type of mollusk and a source of colorful mother of pearl. They're mostly harvested for food by humans, but shells have been found in archaeological sites as far back as 100,000 years ago.

1. Red snapper
   Sea bass
2. Perch
   Flying fish

Flying fish, like flying squirrels, don't fly so much as glide when they get in the air. That said, flying fish are pretty amazing at gliding. They've been clocked at 45 seconds worth of flight time and covering distances of up to 1,300 feet.

1. Tiger shark
   Great white shark
2. Mako shark
   Thresher shark

Great white sharks have suffered a lot of bad press because of the movie "Jaws." Though they have no natural predators besides the odd killer whale attack and they have attacked humans in the past, that accounts for less than 300 total attacks.

1. Sei whales
   Beluga whales
2. Bottlenose dolphins
   Humpback whales

Humpback whales are one of the most social whales when it comes to humans and are often known to breach when humans are in boats near them, sometimes right under people in smaller boats. As such, they're a favorite of whale watchers.

1. Blue lobster
   Giant isopod
2. Yeti crab
   Sea slug

Isopods are what you might know as woodlice or roly polies. In the water, however, giant isopods grow to be a dramatic size. While an isopod in your garden might be 1 inch in length, giant ones from the sea can reach 19 inches or so.

1. Sardines
   Pistol shrimp
2. Krill
   Plankton

Krill are tiny crustaceans that, despite their small size, live in a stunning abundance in the sea. For instance, it's estimated that there are about 379,000,000 tonnes of Antarctic krill in the Antarctic Ocean alone.

1. Unicornfish
   Green krait
2. Roman's seahorse
   Leafy seadragon

The leafy seadragon is a kind of seahorse and also just an exceptionally cool looking little creature. All of those bits hanging off of its body are purely for cover, none of them are fins that help it move in the water.

1. Oarfish
   Viperfish
2. Mahi-mahi
   Snubfish

Extremely common in places like Hawaii, the mahi-mahi is a surface-dwelling fish that gets its name from the Hawaiian language. It means "very strong," and they're extremely popular among sport fishermen in the area.

1. Cuttlefish
   Nautilus
2. Pygmy squid
   Abalone

The very unusual Nautiluses have a unique and cool method of swimming around in the sea. They draw water into something called a hyponome and shoot it back out again, creating a form of biological jet propulsion.

1. Beaked sea snake
   Conger eel
2. Tube worm
   Water moccasin

The beaked sea snake is one of the deadliest if not the deadliest in the world. Upwards of 50% to 90% of all sea snake bites are from this species, and the majority of deaths are also caused by them as well.

1. Tube worms
   Barnacles
2. Zebra mussels
   Plankton

Plankton is a catch-all term for a wide range of tiny creatures, many of them microscopic that basically just float in place because they can't swim against the current. Plankton is the base of the food chain in the ocean.

1. Tube worms
   Oarfish
2. Sea kraits
   Electric eels

Oarfish can grow to an extraordinary length of 18 feet, making them the longest bony fish in the world. Despite how that makes it seem like they'd be a target of trophy anglers, they're rarely ever caught alive and they're not suitable for eating as their flesh is weirdly jelly-like.

1. Walrus
   Dugong
2. Manatee
   Ribbon seal

No other seal species is as visually striking as the ribbon seal with its stark black and white coloration. They spend nearly their entire lives at sea and surface on ice floes sometimes but rarely on actual land. Because they're so far from human habitation, they're one of the least studied species.

1. Blue mussels
   Geoduck
2. Razor clam
   Green oysters

Blue mussels are one of the most common mussels in the world and are actually known as common mussels as well. They're harvested in most of the world's oceans and are used in a wide variety of seafood dishes.

1. Conger eel
   Olive sea snake
2. Nautilus
   Giant tube worm

Giant tube worms create large mineral tubes around their bodies as a form of protection and can grow to lengths of nearly 8 feet. They live deep down on the ocean floor near hydrothermal vents called black smokers.

1. Red porgy
   Yellow perch
2. Pike
   John Dory

John Dory is a widely fishes species that shows up on menus from time to time. The unusual name seems like it should have an easy explanation, but it doesn't. The origin is a mystery with several competing theories about where it came from.

1. Barracuda
   Devilfish
2. Viperfish
   Murkfin

Viperfish are about 1 to 2 feet in length, which doesn't seem too extreme at first, but their terrifying jaws with massive, needle-like teeth make them quite intimidating. They're also coated in a thick slime that has yet to be identified.

1. Sei whale
   Walrus
2. Unicorn fish
   Narwhal

Narwhals can be found in the very cold Arctic waters in places like Greenland and Canada. That horn on their heads is actually a tooth that grows from inside their mouths and pierces out through the skin.

1. Sawfish
   Nurse shark
2. Mako shark
   Barracuda

Sawfish can grow to an impressive 25 feet in length, a large portion of that just being the saw on their faces. That saw is a protrusion from the skull made of cartilage. They use the saw to sweep through the ocean floor and stir up prey.