"This is Silfra, in Iceland, where I got to swim between two continental plates.
"On one side of me is the North American plate.
"On the other side is the Eurasian plate.
"And here, this is where they're very slowly tearing apart."
Every word I said there was technically true.
And I don't want this video to take away from the magic:
swimming in Silfra was incredible, my guides were great, I'd recommend it.
But here's the thing: this is the Bridge Between Continents,
it's about 100km southwest of there, and it also claims
to be the point where the two continental plates are breaking apart.
And the two cracks, this and Silfra,
they aren't connected.
Not to each other, and not to the countless other cracks like them across Iceland.
Now, the last time I did a video like this, a few people got angry at me.
Because yes, I'm about to debunk something,
and if you have fond memories of diving or snorkeling between continents,
or holding up this bridge in a photo,
this might make it a little less magical.
Particularly if you we able to dive deep enough at Silfra
to get the photo where you touch both sides at the same time.
"You need to be a qualified diver to head down into the depths.
"I'm not, so I'm staying up there on the surface with a snorkel.
"And yes, my camera lens keeps fogging up,
"I tried to do a piece to camera while I was in the water
"but it didn't go well."
[unintelligible wet microphone noises]
Here's what true: Silfra is a crack in the earth,
and it is between two tectonic plates. Absolutely.
If you're diving there, you are 100% diving in between the continents.
The bit that doesn't hold up is:
that's not The Dividing Line.
You've not got A Different Tectonic Plate on each side of you,
you're just in the bit where they split apart.
A good way of thinking about it is:
imagine that this bridge really was between the continental plates.
Imagine that really was the American plate,
and this really was the Eurasian plate.
What would this be, down below?
I mean, other than a lot of volcanic sand that's getting in my shoes.
Is it neither? Both? A bit in between?
Whatever this is, it's true for this whole area, for kilometres.
You can see that on the map in the bridge.
This is just one of many places where the rocks happened to be a little bit weaker,
so this is where they broke in two to let this whole area... stretch.
Plate tectonics is messy and three-dimensional.
This is just where it looks dramatic.
As you move out of this area, east or west, over kilometres,
the cracks become fewer and fewer, and less and less common,
and then they stop, and then you can definitely say you're on one of the continental plates.
But this bridge is symbolic. Silfra is symbolic.
It's where one of the cracks happened to breach an underground river.
But swimming in Silfra is still an incredible experience, and here's why.
"Silfra is filled with glacial meltwater, an underground river surfacing there,
"the water has been been filtered for decades through rock.
"And there's so much of it that there's a constant current
"pushing any impurities out into the nearby lake.
"Which includes me.
"I'm swimming in a literal river of mineral water, and the visibility is perfect.
"In other parts of Iceland, water like that is bottled and sold.
"But here, we're inside Þingvellir National Park,
"which was the home of the Icelandic Parliament for eight centuries
"and is the most historic part of the entire country.
"So, no bottling plants there.
"And because it's glacial meltwater,
"it's also only just above freezing point, about 2-3°C,
"so I need to wear a dry suit to prevent hypothermia."
Swimming in Silfra is, technically, swimming between the continents.
That is true.
And if there's been one theme through my videos over the years,
it's been that the real world does not fit into the neat little boxes that we'd like it to.
Even though we keep designing systems that have strict categories and sharp dividing lines,
there are always exceptions.
The continents don't split at a single line.
The real world is far more messy than we often think.