According to geology.com, Russia's Lake Biakal has as much water as the five great lakes combined.
Seventy-one percent of the Earth's surface is covered by water, but most of that's saltwater, what's fresh only accounts for about three percent and most of that is trapped in the ice sheets of Antarctica.
Still, freshwater plays an incredibly important role in life as we know it.
Though it's considered a renewable resource, it has its limits.
Two of the biggest threats to freshwater are pollution and overuse.
In an effort to preserve it by encouraging people to use less of it, a biologist in South Africa has utilized an unexpected tool, his camera.
Rivers really are the arteries of our planet.
They transport cool, clean water from the mountains, down across landscapes and give us this critical resource that we rely on so heavily for drinking, for farming, for industry, without these arteries bringing us clean water we'll be in trouble.
Jeremy Shelton is a biologist and photographer at the Freshwater Research Center in South Africa.
A world wildlife reports of freshwater fish featured Shelton's images which caught the attention of actor and activist Leonardo DiCaprio who shared them on Instagram.
It's all about inspiring people to become more aware of the natural world around them.
Being able to take these snapshots, bring them above the surface, share them with people that have never had a chance to see this world that I care so much about and once that connection is forged to change the way they behave.
More than half of all fish live in freshwater environments, which are increasingly under pressure from a variety of threats including climate change, pollution and invasive alien species.
Behind me here, you can see the Rondegat River, a beautiful mountain stream here in the Cederburg Mountains and this is actually the site of the first freshwater fish restoration project here in South Africa, where alien freshwater fishes were removed to create room for indigenous species that were running out of habitat in the wild.
A big conservation game for freshwater ecosystems in South Africa.
The stability of our planet is intimately linked to having healthy, functioning ecosystems, whether it's the forests that take a lot of their carbon dioxide out of our atmosphere or the freshwater ecosystem that really feed those forests and allow them to grow.
It's all connected and it's really in our best interest to ensure that all of these different kinds of ecosystems stay as healthy as possible for as long as possible.
The situation is urgent. In 2018, South Africa released a report on biodiversity which revealed that freshwater fish were the most threatened species group in the country.
Shelton is determined to do all he can to save these precious resources.
I'm hoping that through connecting with this previously unseen world that people will treat them a little bit more gently.
That people will be a little bit more thoughtful about the way we live our lives and about the way we interact with these natural ecosystems.
Whether it's taking a shorter shower or accessing rainwater, or brushing our teeth for a minute less.
Every little bit of water saving can help.
The conservation needs for freshwater life are extremely high and it's really reaching a tipping point now where it's take action or we stand to lose a lot of these species and the ecosystems in which they evolve.