The planet is about 70% water — and Australians should know that better than most.
But there are some interesting rules for how bodies of water are named.
Why is this called an ocean, and this a sea?
What makes this a gulf, and this a bay?
We’ll start big.
Oceans are large bodies of saltwater which surround continents.
Australia’s in between the Pacific, Indian and Southern ocean.
Oceans are generally divided between continents, but technically it’s one big body of water
— sometimes referred to as the World Ocean.
Seas are large bodies of saltwater connected to the ocean, but they’re also partly surrounded
by land, like the Tasman or Coral Sea.
At the top end of Australia you’ll find a gulf, a large body of water enclosed by
land on three sides, with a relatively narrow opening.
Down the other end, you’ll find the Great Australian Bight.
A bight is an inward bend in a coastline or a river - less of a deep indentation than a gulf.
And right next to this bight is this strait — a narrow passage of water connecting two
large bodies of water.
Bass Strait separates Tassie and Victoria.
Torres Strait Islanders are from, you guessed it, the Torres Strait.
Let’s swing by Sydney.
Here you’ll find heaps of bays.
They’re like the smaller siblings of gulfs, but with a wide mouth.
And small bays are called coves.
They’re often sheltered between rocky headlands.
Of course, you can’t think of Sydney without thinking of Sydney Harbour.
A harbour is a body of water along the shore deep enough for ships to moor, and protected
from rough water and winds.
But if you want to get technical, Sydney Harbour is really a drowned river valley, which is
a type of estuary.
That’s what you call a body of water where rivers meet the sea.
Let’s leave the coast and go west, where we’ll find the Murray River.
A river is a large natural waterway which flows from higher to lower ground.
A stream is a smaller river — not as deep, long or wide.
Small streams are called creeks, and smaller still are brooks.
If you track a large river to its source, along the way you’ll find tributaries — these
are streams that feed into larger streams or rivers.
If we head over into South Australia, we’ll find something else that tributaries feed
— lakes.
They’re bodies of water surrounded by land.
They’re usually freshwater, but sometimes they can be saltwater (more on that later).
A lagoon is a small lake, but formed near coastal areas.
They’re separated from the ocean or a sea with reefs or a low sandbank.
Going up to the Kimberley, we’ll find something really Australian — a billabong.
These are small lakes formed when a river changes course and leaves a body of water behind.
They’re sometimes reconnected to the river during flood periods.
The word “billabong” is based on a Wiradjuri word, literally meaning “a channel which
runs only after rain”.
In other parts of the world, a billabong is called an oxbow lake.
Heading back east, you’ll find a massive swamp called the Arafura.
A swamp is a forested area of low-lying land covered in stagnant water.
You’ll often find them near a river or lake.
A swamp without the trees is called a marsh.
Bogs are similar to swamps and marshes, but they can’t support large plant life.
Over in Queensland you’ll find a claypan.
It’s basically all in the name — it’s a shallow depression in the ground with a
hardened clay base.
Back towards the coast there are plenty of tide pools — rocky ocean pools filled with
seawater.
Springs, on the other hand, are filled with groundwater flowing out of the ground.
These are all widely agreed upon naming conventions, but there are plenty of interesting exceptions
around the world.
The Caspian Sea is entirely landlocked, and its saltwater is diluted from the freshwater
tributaries flowing into it.
So you could call it a lake.
But basically, before we had clearer definitions for these things, people noticed it was big
body of saltwater — so they called it a sea.
Just like how the Gulf of Thailand should be way bigger than the Bay of Bengal, how
Baffin Bay is really technically a sea, and how the Sea of Galilee is quite obviously
a lake.
The names have stuck, so here we are today.
Here’s a fun fact: A Sydharb is actually an unofficial Australian unit of measurement.
It’s used to measure volume of water, obviously, and one Sydharb is equivalent to about 0.5
cubic kilometres - the amount of water in Sydney Harbour.