Jeff Probst explains how two players beat a Survivor challenge

Even 43 seasons in, Survivor continues to surprise. History was made in the most unlikely of fashions on Wednesday's episode of Survivor 43 when the reality franchise staged one of its most famous — and famously brutal — challenges in Fiji for the first time. And somehow, two players managed to do the seemingly impossible and beat the challenge.

The Last Gasp challenge was first unleashed back in season 10 (Survivor: Palau) as a contest in which players had to lie in the water for as long as they could under a graded steel barrier. Sounds easy, right? But then the tide would come in. And the claustrophobia would set in. And the water level would rise to the point where seawater was covering the players' mouths and going up their noses. It was a horror movie come to life. It was awesome.

Survivor brought the challenge back for only the fourth time ever on Wednesday's episode, and the conditions appeared to be more brutal than ever. Not only did the players have to contend with the rising tides, but there were big swells that would completely submerge the contestants for prolonged periods of time. And yet somehow, some way, two people fought through it all.

CBS The cast of 'Survivor 43'

Karla Cruz Godoy and Owen Knight morphed into Poseidon and Aquaman, lasting for almost three hours as the tide got higher and higher… and then lower and lower, until there was no more tide coming in to contend with. In a historic decision, host Jeff Probst eventually called the competition and awarded each player immunity, since there was no conceivable tiebreaker after such a brutal competition.

EW got in touch with Probst to get the behind-the-scenes story on how this epic challenge and historic result unfolded.

ENTERTAINMENT WEEKLY: Last Gasp is one of the most famous Survivor challenges ever, yet had only been run three times, and never before in Fiji, because it is so difficult to get the right conditions for it. How were you all able to finally stage it out there?

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. It's all about the ability to overcome the claustrophobic fear that consumes you as the tide rises and your ability to breathe becomes more difficult.

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… until Survivor 43! The minute [challenge producer] John Kirhoffer heard we had landed a new location that offered calm water, he put Last Gasp onto the board!

CBS Jeff Probst and the cast of 'Survivor 43'

As you mentioned on the show, tides are always different, but roughly how long were people lasting in the challenge tests you all did before running it for real?

The tests we did with our Dream Team varied because the tides are always slightly different. Usually our Dream Team provides a pretty good approximation of what we can expect, but in this case nobody came close to lasting as long as Karla and Owen.

At what point did you start to consider calling the challenge, and what was the final time when you all finally called it?

Last Gasp is a unique challenge in the sense that there isn't much drama in the early stages because you're simply waiting for the water to rise. 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. Once Cassidy dropped out at just over two hours, I started focusing on the showdown between Karla and Owen. 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. I could feel the panic and was looking for signs of who was going to finally give up and pop to the surface.

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? But it had to be because the water was clearly higher than the challenge structure, and that was our marker that we were near the end.

CBS Owen Knight on 'Survivor 43'

I stayed focused on the drama. I knew that any second now, someone was going to finally succumb to one of the most physically and emotionally draining challenges in our Survivor arsenal. 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.

Once the water receded enough that both Karla and Owen could hear me, we announced that they had outlasted our challenge and both would be safe at Tribal Council. Two hours and 50 minutes after we began, the challenge was called, and history was made.

Because I care about stupid stuff like this, did someone have to go retrieve and bring the second immunity necklace, or did you have it on hand just in case?

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

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