1. Humpback Whale
   Blue Whale
2. Sperm Whale
   Narwhal

Blue whales are not just the largest species of whale, they're the largest species of anything. A blue whale can exceed 100 feet in length and weigh over 150 tons, which means, at an average weight of 200 pounds, you'd need 1,500 adult men to equal the weight of one blue whale.

1. Sea Mink
   Right Whale
2. Amazonian Manatee
   Irrawaddy Dolphin

The Irrawaddy Dolphin is an odd-looking creature that could probably pass for a beluga whale in a pinch. They're usually remarkably slow swimmers but can zip up to about 25 mph when they're feeling threatened.

1. Walrus
   Sea Lion
2. Sea Otter
   New Zealand Fur Seal

Walruses can be found in the Pacific, Atlantic, and Arctic regions which represent the three subspecies of the animal. An adult male walrus can weigh around 4,000 pounds and about 12 pounds of that could be nothing but tusk.

1. White Bear
   Arctic Bear
2. Polar Bear
   Sun Bear

The polar bear is the largest land predator in North America and also the largest of the bear species. They are terrestrial creatures but they're well adapted to the water and have huge, paddle-like paws that help them swim.

1. Beluga Whale
   Humpback Whale
2. Gray Whale
   Orca

Humpback whales are one of the larger whale species, often measuring up to 60 feet and over 40 tons. Despite that huge size, they're pretty agile and even acrobatic. Whale watching tours exist just so you can see these massive beasts leaping out of the water.

1. Blainville's beaked whale
   Dugong
2. False killer whale
   Harbor porpoise

Blainville's beaked whale was named by French zoologist Henri de Blainville. Like most beaked whales these animals aren't all that well-studied so many of their habits aren't well known but they do tend to have large, barnacle-encrusted teeth.

1. Killer Whale
   Narwhal
2. Beluga Whale
   Minke Whale

Beluga whales are a common sight at aquariums around the world as they're one of the smallest whale species. They're also very social animals and will travel in groups where they click and whistle frequently at one another, communicating whatever it is whales need to communicate.

1. Bryde's Whale
   Sei Whale
2. Gray Whale
   Bowhead Whale

Bowhead Whales are one of the largest whale species and can clock in at 100 tons. They have the thickest blubber of any whale species in the world which can get up to a staggering 19 inches in some places.

1. Omura's Whale
   Fin Whale
2. Sei Whale
   Minke Whale

At 90 feet long and 100 tons, fin whales don't have a lot of things to worry about in the sea aside from humans. Unlike some species, fin whales don't often travel in large groups and can be found either in very small pods or even alone.

1. Dugong
   Sea Otter
2. Harbor Seal
   Walrus

Dugongs and manatees are very closely related but not quite the same animal. How do you tell the difference between the two? There are a few ways but the easiest and most noticeable is the tail. A dugong tail looks almost like a dolphin's tail while manatees have more of a rudder-like tail.

1. Harbor Porpoise
   Bottlenose Dolphin
2. False Killer Whale
   Right Whale

The harbor porpoise gets its name from its tendency to stay in and around harbors. Full grown they're about the size of an adult male human, measuring about 6 feet long and 200 pounds or so. In this species, the females get a bit bigger than males.

1. Perrin's Beaked Whale
   Risso's Dolphin
2. Amazon River Dolphin
   Costero Dolphin

The Amazon river dolphin or "pink river dolphin," as it's sometimes called, is the largest river dolphin species in the world, even though it's rather small compared to whales. Not all river dolphins are pink. They can appear in an array of colors including gray, yellow and brown.

1. Sea Otter
   Fur Seal
2. Narwhal
   Walrus

The sea otter is the largest member of the weasel family and can almost get up to 100 pounds. They have no blubber to keep them warm and rely exclusively on their incredible fur which grows at a density of nearly one million hairs per square inch.

1. Orca Whale
   Gray Whale
2. Pygmy Right Whale
   Vaquita

Vaquita means "little cow" and these relatively tiny animals are sadly not nearly as plentiful as cows. There are no solid numbers on vaquita population right now but it's believed there are literally only a couple dozen of these animals in the world.

1. Sea Cow
   Stellar's Sea Lion
2. Manatee
   Harbor Seal

Stellar's sea lion is one of several different sea lion species that are very similar to seals but not quite the same thing. If you can't tell the difference between a seal and a sea lion at first glance, look for the ears. Sea lions have them and seals do not.

1. Spectacled Porpoise
   False Killer Whale
2. Dall's Porpoise
   Right Whale

Dall's porpoises live in the North Pacific and are fairly widely hunted. Though they are not listed as endangered, there is a lot of international attention to the hunts that allow for the killing of these animals as they're also greatly at risk as by-catch from salmon fishing.

1. Gray Whale
   Orca Whale
2. Narwhal
   Bryde's Whale

Bryde's whale is closely related to the sei whale and the two are often confused with one another. In Japan, these whales used to be called anchovy whales because they tended to hunt a lot of anchovy in that part of the world.

1. Blue Whale
   Gray Whale
2. True's Beaked Whale
   Dusky Dolphin

Gray whales are a large species that can get to be about 50 feet and 40 tons. A female gray whale has been credited with the world's longest round-trip migration after it traveled more than 13,600 miles in 2015.

1. Narwhal
   Beluga Whale
2. Orca Whale
   Bottlenose Dolphin

Bottlenose dolphins are one of the most recognizable animals in the world. They're known for their intelligence and their playfulness as well as their unusual curiosity which makes them eager to approach human every so often.

1. Sperm Whale
   Narwhal
2. Sei Whale
   Right Whale

The sperm whale gets its name from the organ in its head that produces a white, waxy substance that was mistaken for sperm by early sailors. These animals are known to have the largest brains of any creature on earth which can weigh up to 17 pounds.

1. Sei Whale
   Omura's Whale
2. Bryde's Whale
   Yangtze River Dolphin

Omura's whale is a fairly rare and poorly studied whale relative to other species. It's also considered small at a mere 38 feet which, compared to the blue whale technically is pretty tiny overall.

1. Galapagos Sea Lion
   Dugong
2. West Indian Manatee
   Sea Otter

The West Indian manatee is also called the American manatee and it's the chubby critter you'll find off the coast of Florida. Rumor has it that, ages ago, when sailors thought they saw mermaids in the surf they may have actually just been seeing these creatures.

1. Pygmy Blue Whale
   Humpback Whale
2. Southern Minke Whale
   North Pacific Right Whale

Population estimates put the entire species of North Pacific Right Whales at around 100 animals or less. They were historically hunted for their meat and oil and their baleen, which is the filter system in their mouths. People used to make corsets out of them.

1. Beluga Whale
   Minke Whale
2. Orca Whale
   Shepherd's Beaked Whale

Minke whales only grow to a length of about 30 feet which is small for baleen whales. Like many whales, they were aggressively hunted for a time and are now a protected species, though that still hasn't stopped some people from killing them.

1. Hooded Seal
   Northern Fur Seal
2. Bearded Seal
   Crabeater Seal

The hooded seal gets its name from the large bladder on the head of the males that hangs down between its eyes. It's not even the only weird sac on this animal as it can also inflate one out of its nostril as well.

1. Sei Whale
   Melon-Headed Whale
2. Right Whale
   Blue Whale

The melon-headed whale is, in fact, a dolphin despite the name. It does have a bit of a round, cone-like head that could pass for a melon if you changed the color of it, hence the unfortunate name it's been saddled with.

1. Sei Whale
   Narwhal
2. Pilot Whale
   Finless Porpoise

The sei whale can grow to be around 30 tons but can still motor along at about 30 miles per hour when it needs to. What's it take to keep an animal this size going at that speed? About 2,000 pounds of food each and every day.

1. Sperm Whale
   Narwhal
2. Orca
   Baird's Beaked Whale

Few mammals in the sea are as well known as the orca. It's been immortalized in film sometimes as a villain as in the movie "Orca: The Killer Whale" but more often as a sympathetic creature like in "Free Willy" and "Blackfish."

1. Orca whale
   Spade-toothed whale
2. Walrus
   Narwhal

Narwhals are a very popular species of whale thanks in part to their very unusual appearance which includes what looks like a single, long horn poking out of their head. In fact, it is not a horn at all but one long tooth that grows from inside the whale's mouth and pushes through from the inside. Some even have two.

1. Peale's Dolphin
   False Killer Whale
2. Rough-Toothed Dolphin
   Pilot Whale

False killer whales don't actually look that much like killer whales but internally they do, specifically the shape of their skulls, which is where the name comes from. Also despite the menacing name, they're pretty sociable animals.

1. Crabeater Seal
   Brown Fur Seal
2. Ringed Seal
   Southern Sea Lion

Crabeater seals are found in the Antarctic and for reasons that only a marine biologist can explain doesn't actually eat crabs. The seal's diet is almost entirely made up of krill, which it can filter through its teeth.

1. Spinner Dolphin
   Finless Porpoise
2. Burrunan Dolphin
   Tucuxi Dolphin

The Burrunan Dolphin is found in Australia and was officially recognized as a species in 2011. The reason it wasn't recognized for so long is mostly that it's only been identified in two locations with a population of about 150.

1. Beluga Whale
   Risso's Dolphin
2. Right Whale
   Finless Porpoise

The finless porpoise might look like a typical porpoise at first glance but the lack of a fin makes it stand out more than any other member of the species. That distinctive back fin that so many aquatic creatures have is missing.

1. Spinner Dolphin
   Harbor Porpoise
2. Hourglass Dolphin
   Dusky Dolphin

Spinner dolphins get their name from their interesting and pretty cool ability to spin like a corkscrew as they jump out of the water. At their best, a spinner dolphin can actually pull off over 5 full rotations before landing back in the water again.

1. Fraser's Dolphin
   Risso's Dolphin
2. Hourglass Dolphin
   Chilean Dolphin

The hourglass dolphin is a small species of dolphin that only grows to about four feet in length. They were first recognized as a species in 1824 based on someone else's drawing of one rather than any real-life identification.

1. Galapagos Fur Seal
   Bearded Seal
2. Ribbon Seal
   Grey Seal

Galapagos fur seals are one of the smallest species of seal with adult males coming in at about 5 feet in length while the females are about a foot shorter. Unlike many seal species, the Galapagos spends as much as 70% of its time on the land.

1. Weddell Seal
   Japanese Sea Lion
2. Southern Elephant Seal
   Harp Seal

The Southern elephant seal is one massive customer as far as marine mammals go. A bull male can weigh nearly 9,000 pounds and grow to a length of nearly 19 feet. The largest on record was 22.5 feet in length and was weighed in pieces at about 11,000 pounds.

1. Pantropical Spotted Dolphin
   Rough-Toothed Dolphin
2. Hector's Dolphin
   Clymene's Dolphin

Pantropical spotted dolphins are a relatively unknown species but they did gain some prominence years ago as part of a conservation effort. Because the dolphins swim with tuna so often, literally millions of them were dying when they were caught up in tuna fishing nets.

1. Melon-Headed Whale
   Pygmy Killer Whale
2. Long-Finned Pilot Whale
   Strap-toothed Whale

Long-finned pilot whales have long, sickle-shaped fins which is where the name comes from. Even though they're called whales, they're actually a very large species of dolphin and can grow to be over 20 feet in length.

1. Harp Seals
   Spotted Seals
2. Rng Seals
   Bearded Sea Lions

Harp seals are famously the face of the controversial seal hunts in Canada. The pups are fluffy, white little critters that are as cute as a bug's ear. Despite worldwide protests, there are government regulated hunts for them every year.