Host Jeff Probst explains how producers handled it on the fly.

Even 43 seasons in,Survivorcontinues to surprise.

And somehow, two players managed to do the seemingly impossible and beat the challenge.

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The cast of ‘Survivor 43’.CBS

Sounds easy, right?

But then the tide would come in.

And the claustrophobia would set in.

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Jeff Probst and the cast of ‘Survivor 43’.CBS

It was a horror movie come to life.

And yet somehow, some way, two people fought through it all.

How were you all able to finally stage it out there?

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Owen Knight on ‘Survivor 43’.CBS

JEFF PROBST:We love Last Gasp.

It is one of a few individual challenges that is pure mind over matter.

There is no discernible advantage based on height, weight, age, gender.

We would do it every season if we could.

But there is one key requirement for Last Gasp.

It requires a protected bay where the water is relatively calm.

For our entire time in Fiji, we’ve been unable to secure such a bay… untilSurvivor 43!

The tests we did with our Dream Team varied because the tides are always slightly different.

But once you get into the nitty-gritty, it becomes incredibly intense.

I have to commend Cody and Cassidy, who both lasted a very long time.

From a challenge standpoint, everything was going great.

The tide was rising, and an epic finish was sure to follow.

There was a period of several minutes where the tide was clearly at its highest point.

The swells were coming faster and faster.

Karla and Owen were having to stay underwater longer before trying to take a breath.

Swell after swell pounded the players, but oddly, neither relented.

It was so surprising that I began to question my own observations.

Was I missing something?

Maybe it wasn’t high tide yet?

I stayed focused on the drama.

But it never happened.

And then there was a very clear moment where I sensed that the tide was beginning to recede.

The swells were getting smaller, and the water level was no longer rising.

This was not something we had anticipated.

I looked across the ocean to our challenge team monitoring from a barge.

It was clear, they were as surprised as I was.

That was when we all started to realize that Karla and Owen may have just outlasted our challenge.

Now it was us, the producers, who were going to have to adapt.

After a moment of considering options, I very subtly held up two fingers to the challenge team.

They gave me an equally subtle nod in agreement.

We had our new plan.

Both players would win immunity.

Two hours and 50 minutes after we began, the challenge was called, and history was made.

We always have an extra immunity necklace with us, so that wasn’t an issue.