The Bay of Fundy in eastern Canada has the highest tides in the world,
anything up to 16 metres difference between low tide and high tide.
And the effects of that show up in a few places around here.
Like Hopewell Rocks, where I'm not standing on a beach right now,
I'm standing on the ocean floor.
That's how far the tide is out.
Actually, I'm kind of sinking into it.
But in a few hours' time,
those rocks will be half-way underwater,
and if I stuck around,
I would be drowning in very cold, very fast and very deep ocean.
But I'm not going to do that!
Instead, I'm going to go about 40km that way, to--
--Moncton. It's the next morning, it's very cold,
and I'm flying a drone to try and get a shot of the tidal bore.
This is one of the few places in the world where, every high tide,
a wave of water washes upstream against the current.
But the most obvious sign of the tides around here is in--
--Saint John, at the Reversing Falls,
where a massive river meets the Bay of Fundy
at a narrow channel filled with rocks and snags.
This isn't just a tidal river: it's a tidal set of rapids.
Calling it a "waterfall" is maybe a bit generous,
but at low tide the water definitely has a gradient,
it drops a couple of metres in height over a really short distance.
And then a few hours later at--
--high tide, the whole flow reverses,
and the river's dropping a few metres in height the other way.
And so the obvious question I had was:
why has nobody turned that bay into a power station yet?
Actually, question number one: why are the tides so high here?
To answer that, I'll use the bathtub in my hotel room.
For this "scientifically-rigorous" demonstration,
the Bay of Fundy is represented by the bathtub,
and the Atlantic tides and all the unimaginable pressure
created by megatonnes of water is represented by...
...my arm. So.
Moon pulls on the ocean, tide comes in, pressure gets applied,
and a wave heads down the bathtub, the Bay of Fundy, and bounces back.
'Cos it's not like the water all rises simultaneously.
It takes time, and yes, the scale here is colossally different,
but you still get a wave effect,
a reflection, and a trough that follows the wave.
Tick, tock. Tick, tock.
And that will always take roughly the same time
to go up and bounce back,
it'll be affected a little bit by the weather and water temperature.
So what happens when the next tide comes in?
If I time each push to go with the wave that's already there,
then very quickly, you start seeing a resonant frequency,
and a lot of power...
Wah!
That worked way better than I expected it to!
The resonant frequency of the Bay of Fundy is roughly 12½ hours,
the same as the tidal cycle. Combine that with geography
that's less like a bathtub and more like a funnel,
getting tighter and tighter as that wave comes in,
and you have the highest tides in the world, right there.
The power is immense and it's obvious.
And if it could be harnessed, then it'd be reliable and renewable.
Intermittent, sure, but on a schedule
that would be simple for the grid to predict and plan around.
So why aren't there tidal power stations all around the Bay of Fundy?
Well, the answer is: it's been tried. A lot. Usually in the--
--Minas Basin, where several companies
have put millions and millions of dollars behind technical trials.
And every time, the Bay of Fundy breaks the turbines!
2009: a turbine was "torn apart".
2010: two blades "broken off".
2018: "damaged beyond repair".
Turbines in these waters have to be light enough to spin,
but strong enough to resist high speed salt water
that carries huge amounts of sediment and big rocks along with it,
and in winter, enormous chunks of sea ice.
Oh, and that's before we even start talking about the concerns
from First Nations peoples and commercial fishing operations
that maybe putting a load of giant spinning things in the water
might cause some problems for fish.
But people are still trying, there are more experimental turbines planned.
Can it be done?
Maybe.
I thought about doing long interviews
with the tidal power companies and their opponents around here,
but those interviews would have sounded the same twenty years ago.
And the result would have just been a much longer way of saying:
maybe.
If it can ever be done, safely and reliably,
it'd be brilliant, I hope that happens.
But there's also a decent chance that the Bay of Fundy
is just going to tear the turbines apart again,
and in twenty years, the answer still will be: maybe.
And now, today's--
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this waterfall changes direction.