However, thanks to intrepid divers armed with expert cameras, we can get a flavour of what lurks below.
The winners of the 7th annual Ocean Art Underwater Photo Contest have just been announced, and the photos are incredibly striking.
They offer a fascinating insight into the creatures of the deep, capturing everything from dolphins to turtles interacting with the camera.
Over $80,000 (roughly R1 million) in prizes have been awarded across 16 different categories, including Wide Angle, Marine Life Behavior, Portrait, Cold Water, and Underwater Art, making the Ocean Art prize value among the highest in the world.
Scroll down to see the breathtaking winners, along with some of our favourite shots from the competition.
The photo captures spinetail devil rays in rarely observed courtship - with two males pursuing one female.
Schiffman says: "I had framed this shot waiting for a sea lion to swim by. After five minutes, one swam up and paused for a few seconds, I took three photos and as rare as it was the moment left in a blink of an eye."
Badten says: "I turned to see this turtle swimming directly at me, which was a truly remarkable behaviour that I have never experienced before. As I set up to capture the unique encounter, the curious turtle saw her reflection and continued to slowly approach until nearly bumping my dome!"
Jones says of the photo: "A lone Sockeye Salmon swims by as wisps of fog cling to the surface in the early dawn hours on the Adams River."
"As I slowly and cautiously watched, I saw this large female sand tiger shark with her own bait ball entourage just approaching the massive ball," says Wallace. "I was mesmerized by the entire scene but my brain quickly engaged enough to set up for the shot of her about to enter."
"These intelligent creatures display so much interesting behaviour and in this case they playfully and curiously swimmed by me," Kitsios says of the image.
"The relationship between the ocellaris clownfish that dwell among the tentacles of Ritteri sea anemones is a good example of mutualism," Visconti says. "The territorial fish protects the anemone from anemone-eating fish, and in turn the stinging tentacles of the anemone protect the clownfish from its predators."
Mane says: "While diving, I noticed above canoes where following my bubbles, it was the end of the day… so here was my opportunity capture the protrait of these kids in their environment - the canoes, the reef, and a stunning sunset as the backdrop."
Mane says: "While diving in Galapagos looking for Mola Mola, we encounter playful Sealions (Zalophus wollebaeki). This particular one used to shake his head side-to-side, like he was saying no for a photograph."
"Stand up paddle boarders were out exploring the shallow reefs at sunset," Thomas says. "I wanted to demonstrate the innate bond humans have with the ocean, whether we are physically in it or floating on the surface."
"This photo took nearly six months to capture with multiple failed attempts along the way," Robins says. "I wanted to capture vivid colours in the sky contrasted with the crystal-clear water and unique formations in the sand below the water's surface. On this particular morning, I was rewarded with an amazing sunrise and crystal clear calm water."
Kujala says: "I was in shallow water, when two Australian sea lion pups swooshed in my direction. They were playing and zipping around each other in what appeared to be a beautiful underwater ballet."
Speaking about his photo, St Jean says: "We were privy to a beautiful, clear, and unoccupied Cenote. As we got our gear on, a light beam appeared in the water from above. Needless to say, we used every second of light to capture photos of this wonderful phenomenon in order to show its mystical beauty."
Sen says: "These Pacific species of salmon will come to the west coast of Canada from the distant sea every autumn. They return to their birthplace by looking for the right salinity of the estuary, the temperature of the river, and the environment of their natal stream."
"While looking for Marine Iguanas at Fernandina Island in Galapagos we came across these inquisitive Galapagos Penguins," according to Lorenz. "Given that they are hunted by many predators above and below the water it was surprising how close they came to us."
Chuang says: "This is my first time to meet jellyfish in Taiwan NorthEast Coast for shore dive! When I did night dive in 2018 summer time, I saw this beautiful jellyfish dancing in the dark."
"Sunset splitshots are fantastic to capture in the shallow reefs of Egypt," Friedrich says. "There are many embankments to look for a nice spot for the perfect lighting from the setting sun."
Gross says: "It was the first dive of a 12-day liveaboard through Flores and Alor, Indonesia. I took a few images at the end of the dive not knowing what the animal was."
Van Saen says: "I was trying to create an image right out of the camera using special own-made backgrounds. But at the end, it was the photoshop filter 'swirl' which helped me a lot to end up with this creative image."
"I found this place which I came back to once a week for four weeks straight and would spend up to 90 minutes each dive in this one little area," Lindbloom says. "It took me a long time figure out what power setting each light needed to be at, where each light needed to be placed, and also figure out how to paint the reef so that I got a nice even 'coat' without over saturating any one area with the light."
Mane says: "A crown jellyfish (Cephea) was under attack. Several speices were predating, but the giant kingfishes where the most resilient hunters looking for juvenile fishes that thought the giant crown jelly would be [a] safe transport vehicle."
Poon says: "We all froze in place, stunned and suddenly ignoring the oceanic manta behind us. One subgroup turned directly in front of me and let me capture their family portrait. The little ones shyly looked around, but their leader watched me closely as they passed."
"On the last day of my 'East of Flores' liveaboard trip, we were diving at Pulau Babi which has a beautiful reef full of soft corals and sponges," Capozzola says. "Because we were diving in the morning, the sloping wall looked up into the sun so I decided to concentrate my entire dive on 'sunbursts.'"
Mane says: "What a panorama - hammerhead sharks are swimming above their heads. The whole dive was dedicated to capture the hills in this unique underwater environment and time the two in the same frame battling currents swimming hammerheads overhead. It was a challenging experience."
Vailati says: "During a dive in Anilao, Philippines I found this nudibranch and I waited for the best time to make this shot."
Zori says the spotted rat fish in this photo is "a resident of the northeastern part of the Pacific Ocean," and "usually lives between 50 and 400 meters and prefers temperatures no higher than 9 degrees. However, it tends to approach in shallow water during the spring and fall."
Cheung says: "I found that another diver, Marissa, was a few meters away from me and behind her was the landmark pinnacle of El Boiler. Visibility was crystal. I thought Marissa, together with the structure of the pinnacle, might be able to create an interesting background showing both the location of the dive site and the scale of the giant manta."
"Hairy shrimp have always been one of my favourite subjects, due to the variety of colors and types of similar species of shrimps," So says. "Shooting a hairy shrimp is also a challenging task due to its tiny size and nature."
Pastrana says: "That morning we saw this crocodile called El Niño. I was told he was nice enough to let you get close to him. He was watching us for quite some time and, when we decided to go in the water, I was nervous but excited."
"This picture offers to the viewer three different versions of this ray," Ropert says. "The subject is always treated in a subjective way, dependent to the photographer's eye and interpretation, in his choice of composition, lighting, and capturing a scene. The reality is multi-faced, we very often grab only a portion of it."
Bavendam says: "Early during the first morning dive on November 12, I found a table of acropora coral with its resident reef fish, damselfish and dascyllus, and was able to squeeze between the coral table and the island's wall, which gave me a blue water background for the picture. As I waited, the baitfish swam by three or four times as they circled the small rock."
Of the experience shooting this image, Baelen says: "This unique encounter happened in September 2018 in Reunion Island (Western Indian Ocean) where the humpback whales come here to breed and give birth. The mother was resting 15 meters down, while her calf was enjoying his new human friends."
"Most enope squids are small and thus difficult to shoot," Milisen says. "As they mature, the difficult paralarva comes into its own. Every detail in the arms, organs, and chromatophores blasts to life in radiant color. Such was the case with this gem of a specimen. At around three inches in length, it was easily the largest and prettiest sharp-eared enope squid I recall finding."
No story was shared for this snap - but it still managed to take first place in its category, "Cold Water."
"Each spring in the cool 15°C water, Big-belly seahorse fry appear in large numbers," Walsh says. "They cling to loose sea grass and weeds near the waters surface, where they hunt in the shelter of the pier. This particular photo is the outcome of four hours of diving between night shifts as a firefighter."
Dudenhofer says: "I have been fortunate enough to have a Japanese guide who showed me a couple of clownfishes with their baby eggs. I never had the chance to shoot this type of interaction before so it was a big challenge for me. The adults swam endlessly around the eggs in order to oxygen them."
Another fan of hairy shrimp, Jang says: "Before this trip, hairy shrimp were on my wish list. Fortunately my dive guide found it for me and my friends. It was my first time to see red hairy shrimp. It's not easy to take photos of it, because it jumps a lot. After this photo, my camera didn't work at all. I'm so lucky at least this nice shot came out of it!"
"It dug its claws deeply into its victim's back, pinning it down before transferring the fresh threads of still living crab meat into its merciless mouth," Hirschfield says. "Between bites, the Cannibal Crab and its hapless victim stared back into my lens - one seeming defiant but justified by its need to feed, the other in all the resigned pathos of the final miserable moments of its life."
Lee says of this image: "A beautiful soft coral anchors and grows on mangrove roots. Two remote strobes were used to highlight the details of mangrove roots in the background, which also provided water surface reflection."
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