Diving into the depthless deep of Earth’s shallowest seas

When looking at the natural world, it often seems that we human beings love nothing more than staring wide-eyed into the abyss, or gazing up at the depths of outer space, desperately straining to try and make out something mysterious and interesting in the inky gloom of a possibly endless void.

But perhaps we’re overlooking something. Maybe the most intriguing treasures in the natural universe are lying, barely covered, in the shallowest waters of our world, not in the deepest darkest depths of the Mariana Trench or in the frozen seas of faraway planets.

At Love Nature, we’ve decided to roll up our trousers only as far as our ankles, and go exploring the shallowest seas on Earth, from the putrid to the pretty. We’ll see what lurks closest to the surface and examine the existential threats that loom over some of the most important, albeit least voluminous, bodies of water around the globe.

Getting grounded

Experiencing vertigo underwater sounds almost violently unnerving, but actually, it feels much more intoxicating than terrifying, if my one brush with the sensation is anything to go by.

It happened when I was diving off the coast of Rarotonga in the Cook Islands. Like the rest of the far-flung and much scattered isles that comprise the Cooks, Raro is basically the top of a volcano, one of a series of brief punctuation marks protruding from the deep purple immensity of the Pacific. It’s sides are super steep, so once you’re a little way off the beach, you are flippering and floundering around in water that’s several kilometres deep.

The deep is a beguiling place, but the Sunlight Zone is where most sea life hangs out.
The deep is a beguiling place, but the Sunlight Zone is where most sea life hangs out.

Scuba diving is all about staying in control—of your actions, of your equipment, of your position and of your reserves of oxygen. When you’re ambling around an octopuses’ garden, floating across a coral reef or bobbing above a bommie, everything is in perspective, and it’s easy to keep an eye on depth and time. Move away from such tangible features and you begin to lose touch with the crucial parameters you must stay within in order not to die.

Beneath the waves in Raro, I found myself magnetically drawn to the drop off, the inverted horizonline where the shelf we were exploring suddenly disappeared and a sheer wall plummeted down into an ever-denser blue.

Sliding over the edge it felt like I was BASE-jumping in slow motion. I only wanted a quick look, but my dive master suddenly appeared wide-eyed next to me, gesticulating furiously at his depth gauge. Minus 45 metres and dropping fast. Oops.

Back on board the boat, I got a bit of a bollocking, but amid all his stern words about losing perspective and how quickly you suck through air at depth, the DM’s most memorable comment was his last: ‘There’s not much to see down there anyway.’

He was right too. For starters, colours disappear one by one as you descend. Red goes first, vanishing not much past 5 metres, followed by orange at 10 metres, yellow at 20 metres and green at 30 metres—beyond this point everything is rendered in shades of increasingly blurry blue, until the light goes out altogether, which can be as deep as 1000 metres.

Of course, things do exist in this monochrome marine world—and mightily alarming looking creatures some of them are too—but they’re very few and far between.

Military and commercial divers descend much deeper than you’re ever supposed venture to as a recreational diver, as do committed cave explorers, but they don’t go down there for wildlife encounters. All the best action happens in the Sunlight Zone, from the surface to 50 metres down. This is where the majority of sea creatures hang out, along with almost all the aquatic flora in the world. And that is where I resolved to stay and play from there on in.

Going to Extremes

It’s natural to feel curious about places you will never reach. The Mariana Trench is a mind-popping 11 kilometres below sea level at its most scarred extent. At 10,994 metres below sea level, Challenger Deep is though to be the very deepest place on Earth.

Humans—including the film director James Cameron—have damn near touched the very bottom, but the vast majority of us will never get anywhere near this dark domain, so it’s easy to imagine a dramatic scene, lined with the broken bones of colossal krakens.

And there very well may be a few colossal squid beaks lying around, because these enigmatic denizens of the deep are believed to do mortal combat with sperm whales in the Midnight Zone above the trench, but mostly it’s just extremely dark and dangerous down there.

Gulf on the Sea of Azov
The Sea of Azov

Meanwhile, at the other extreme, anyone can dip their toes into the Sea of Azov in southeastern Europe, and go exploring the world’s shallowest sea, which varies in depth from 0.9 to 14 metres.

Squeezed between the Ukraine (to the north) and Russia (to the east), with the hotly contested Crimean Peninsula on its western shore, the Sea of Azov doesn’t always have calm waters in the political sense, but it does play home to a reasonably rich variety of wildlife. Azov is connected to the Black Sea by the narrow Strait of Kerch, and the two bodies of water share plenty of biodiversity, including species of shark (spurdog and catfish), seal (grey) and dolphin.

Not so long ago, three distinct types of dolphin were known to cavort in the shallow waters of the Sea of Azov—the short-beaked common dolphin, common bottlenose dolphin and harbour porpoise—with the latter even being referred to as the Azov dolphin by Russians. Now, with the sea becoming even shallower as silt and pollution is washed in from the Don and Kuban rivers, and fish stocks running low, dolphins are spotted far less often.

Silting isn’t a major negative for all wildlife, though. In some ways, the Sea of Azov is defined by its numerous spits, which are formed by sediment washed into the basin from its feeder rivers. A haven for many species of sea birds and wading fowl, several of these are national nature reserves, including Beglitsk, Belosaraysk, Krivaya, and Berdyansk Spits.

On the western bank of the Sea of Azov, separated by the skinny Arabat Spit but fed by the Henichesk Strait, is a delightful sounding stretch of water known as the Putrid or Rotten Sea. With a maximum depth of just three metres, Syvash (or Sivash) as locals call it—depending on whether they’re on the Ukranian or Russian side of the spiky fence—truly is the world’s shallowest sea, if you accept that it’s a sea at all.

Many view it as simply a series of connected lagoons that spread across 10,000 sq km, but either way, its rather unfortunate name can be blamed squarely on the shallowness of the water, which evaporates in the summer leaving vast swathes of stinky swamps.

Luckily, birds don’t seem to mind the malodorous honk one bit. The Syvash is a wetland of international importance and the entire area is protected within the boundaries of the Azov-Syvash National Park.

The park sprawls across a total area of 52,000 hectares, of which 43,685 hectares are covered by the thin waters of the Azov Sea, Syvash Lake and the Utlyutskyy Estuary. Salinity is high—too high for most fish, which only live in the eastern parts of the Syvash—but amid a profusion of bacteria, algae and invertebrates, over 100 species of bird make a living here, including pelicans and cormorants.

Other fauna is relatively abundant too—indigenous and introduced—including hares, foxes, raccoon dogs, red and fallow deer, mouflon, kulan and wild horses, which populate the 8469 hectares of parkland that does stay dry, including Byriuchyi (‘Wolf’) Island.

Low Volume, High Stakes

While the rest of the planet fears the threat of rising sea levels caused by global warming, which will swamp low-lying settlements and wildlife habitats around the globe if almost universally held predictions turn out to be true, shallow seas face another even more immediate existential threat: they could simply disappear altogether, as feeder rivers are dammed, canals are constructed and water is redirected for industrial use.

According to scientific reports, the levels of freshwater now flowing into the Azov have already been reduced by a third, and unmanaged water abstraction is heightening the problem, putting the sea’s ecosystems at extreme risk.

On top of that, there is a proposal to expand the Manych Ship Canal into a much larger Eurasia Canal, linking the Azov and Black seas to the Caspian with an umbilicus navigable by massive commercial shipping. If it goes ahead, this could have profound consequences for the resident wildlife species that inhabit of all of these inland seas, with salinity levels possibly affected and the potential for mass contamination from oil tanker spills introduced into the equation.

Sunset over the Caspian Sea.
Sunset over the Caspian Sea.

Currently, the Caspian Sea, to the east of the Sea of Azov, is one of the more resilient of the region’s bodies of water. This vast puddle is home to the largest fresh water fish in the world, the beluga sturgeon (which can reach five metres in length), and other ultra intriguing inhabitants such as the Caspian seal and the spur-thighed tortoise.

Colourfully encircled by Azerbaijan, Iran, Kazakhstan, Russia, and Turkmenistan, the Caspian divides opinions and sparks arguments—not so much over national borders, but among pub quiz contestants. Is it a sea, or a lake?

With a surface area of 371,000 sq km, this enormous endorheic basin (meaning that it has no outflows) holds over three-and-a-half times the combined volume of water of all five of North America’s Great Lakes. Fed by over 130 rivers, its water is, on average, only about a third as salty as typical seawater, and for all of these reasons, the Caspian is commonly claimed to be the world’s biggest lake. If accepted as such, then it boasts up to 44 per cent of all the lacustrine waters in the entire world.

But although its salinity may be comparatively low, it is still a body of saltwater, and so most people accept that the Caspian is an inland sea, rather than a gigantic lake. In truth (as in nature), though, you may as well accept that not everything can be neatly pigeonholed, and it’s probably most accurately described as a bit of both.

The sea/lake has three parts to it—Northern, Middle and Southern. The Northern Caspian is the shallowest most lake-like section, with an average depth of only five to six metres. This part is so shallow that it regularly freezes over during winter, but by the time you get to the deep end of the Caspian Sea in the South (no armbands or non swimmers allowed, kids must be supervised by responsible adult), the bottom can be more than 1,000 metres below the surface.

And it’s this greater depth that provides the Caspian with a generous insurance policy, protecting it against the tragedy that afflicted its sister sea, the Aral, further off to the east—the sorry fate of which is the scariest cautionary tale in many environmentalists’ big book of horror stories.

When I was born, the Aral Sea was generally considered the fourth biggest inland sea on the planet. With water stretching across more than 67,000 sq km, sizeable ships regularly sailed 400km from Muynak in Uzbekistan to Aralsk in Kazakhstan. By the time I was alarming my dive master off the coast of the Cooks, aged around 40, it had virtually disappeared, shrinking to just 10% of its original extent, with the remaining water divided first into three, and then (when the eastern sea gave up the ghost in October 2014) two separate lakes, neither of which now trouble the top 100 list.

Satellite images of the Aral Sea in 2000 (on the left) and 2014 on the right. Photograph: NASA
Satellite images of the Aral Sea in 2000 (on the left) and 2014 on the right. Photograph: NASA

Prior to the 1970s the Aral Sea had a thriving fishing industry—one that supplied a sixth of the Russian market. Now, men who used to take off on fishing expeditions from outside their front door, live in the middle of a desert, with their ruined ships left high and dry where the sea used to be. They haven’t moved, but the water has. In fact it’s pretty much gone altogether, and camels now walk where carp and caviar-rich sturgeon once swam.

In the space of four decades, around 60,000 sq km of water—in places up to 40 metres deep—has dried up. At the same time, billions of litres of fresh water that would have replaced it was siphoned off from Central Asia’s two biggest rivers—the Syr Darya and the Amu Darya, which both used to feed the Aral Sea—to irrigate the vast Soviet cotton industry being developed across Uzbekistan.

Eventually, the Amu Darya stopped flowing into the Aral altogether. As evaporation continued apace, salinity rose and the sea became increasingly polluted, until all the remaining fish simply went belly up, fouling the water even more. Then, as the basin emptied, the entire region became arid, completely unable to support the crops that once grew in abundance along the sea’s shores and the wildlife that called the Aral area home.

Shallow Silver Linings

There is, though, still some hope that the last remaining puddles of this embattled sea will not only survive, but might even bounce back from the brink, and that fishing and wildlife spotting may one day be viable pursuits once again in the Aral.

Because, at the Kazakhstan end of the former sea, the so-called Small Aral has actually begun to fill up once more. It’s still being fed by the Syr Darya, which helps (even if the river is a mere shadow of the fast-flowing torrent that once stopped Alexander the Great’s army in its tracks).

But the hand of man has also finally been employed in a way that specifically assists the revival, with the construction of a dam to stop all the water running into the sands of the desert. The Kokaral Dam cost a cool $85 million, some of which came from the Kazakh government, who were helped out by the World Bank (which clearly recognises its enormous net worth to the region).

In its heyday, 180 native land-animal species lived around the Aral, and 24 types of native fish swam in its shallow waters. Only a handful of all these species have survived, but they’re staging a comeback. And you’re still more likely to see a great diversity of natural life here than in the Mariana Trench—not least because you don’t need a torch and a submarine.