Often lurking thousands of feet below the ocean's surface are creatures that sometimes don't look like they should be on land.
Humans are becoming well acquainted with these alien-like creatures with the help of increasingly sophisticated underwater robots.
Bareilly fish
This fearsome creature, known as the barrel fish, lives at depths of up to 1 kilometer (3,280 feet) in the North Pacific Ocean, where light rarely touches it.
The bright green orbs that can be seen through the translucent dome on his forehead are his eyes.
It's one of the strangest fish in the world, and was captured on camera by researchers at the Monterey Bay Aquarium Research Institute (MBARI) earlier this year.
With its translucent skull and glowing green eyes, the barrel-eyed specializes in stealing prey from jellyfish.
Their tubular eyes resemble small binoculars, with tunnel vision that can focus on fine details.
The barrel eye, also known as the micropina macropina, is only a few centimeters long.
Bigfin squid
The rarely seen large squid and its 13-foot-long tentacles were photographed by an underwater camera 20,000 feet below the ocean's surface earlier this year.
They are known for their long tentacles, which can reach up to 26 feet in length.
Only about a dozen sightings of them have been confirmed worldwide.
Researchers found this terrifying creature after lowering a camera to the bottom of the Tonga Trench in the South Pacific Ocean.
“We always hope to see this type of animal,” Alan Jamieson, a professor and bathologist at the University of Western Australia, who collected the footage, told Live Science in an email in late September.
“[Bigfin squid] “They're not something you'd actively look for, they're creatures that depend on us coming across them by chance.”
Most documented large squid sightings are “chance photography from oil and gas activities,” Jamieson said.
Jellyfish dinner plate
The dinner plate jellyfish, also known as Solmissus sp., is one of the most dominant predators of the deep ocean.
She has a somewhat unfussy appetite.
“This dweller of the depths has an appetite for other gelatinous animals. Jellies, comb jellies, siphonophores, salinas – they are all on the menu of Solmissus,” researchers at MBARI said in an Instagram post.
“In fact, these jellyfish have one of the most diverse diets of all mesopelagic animals – so far, we've seen Solmisus eat 21 different types of gelatinous prey.”
A hungry jellyfish swims into a dinner plate with tentacles raised forward to catch its prey by surprise.
“Forward-facing claws also help Dinner Plate catch animals with long claws or slender bodies, such as gathering twigs in the grass,” the MBARI researchers noted.
Basketball star
Floating on top of coral or rocks, this strange-looking creature looks like it was pulled from the Pans labrinth.
Their swirling arms, which can sometimes look like tree roots or fern leaves, are used to capture food such as zooplankton.
These branches then funnel food toward its mouth, below the star's central disk, according to the MBARI researchers.
These deep-sea creatures can live up to 35 years and weigh up to 11 pounds.
Giant sea spider
With eight long, slender legs, this fearsome reptile, known as the Giant Sea Spider, clings to the bottom of the deep sea.
While they lurk at depths between 2,200 meters and 4,000 meters (7,200 ft – 13,100 ft), these creatures can be found all over the world.
“Instead of spinning a fine web of silk to catch prey, the giant sea spider uses a rectangular, tube-like proboscis to capture its prey,” according to researchers at MBARI.
It feeds on creatures such as sea anemones, hydroids, jellies and other invertebrates.
The spider, whose official name is Colossendeis sp., can reach up to 20 inches (51 cm) in length, which is much larger than its ground-dwelling cousins.
In comparison, the Goliath birdeater – the largest spider on Earth – has a body length of about 13cm.