Narrator (8:16)
On May 2, 2000, at approximately midnight Eastern Standard Time, the US government discontinued its use of selective availability. Selective availability was the intentional degradation of public GPS signals. It guaranteed that civilian GPS users would not be able to pinpoint locations on a map. Using their GPS, they could get to within maybe 50 to 100 meters, but that was the best they could do. Prior to the year 2000, there was some concern that if you gave the general public the ability to use GPS to precisely locate things on a map, that that presented an elevated national security risk. But that line of thinking became antiquated. And so, on May 2nd, just after midnight, the so called great blue switch, as GPS enthusiasts refer to it, was flipped. And instantly tens of thousands of GPS receivers received this incredible upgrade. People who were following this development were eager to test out this new capability. And one such GPS enthusiast, a guy named Dave Ulmer, who lived in Oregon, decided he wanted to create a sort of GPS treasure hunt. So he got this box, and inside of it he put a notebook and a pen, and he brought it out to the middle of the woods in Oregon, and he got the precise GPS coordinates of where he put it. And he took those coordinates and he went to an online forum and he posted the coordinates. And he said, go to these coordinates and when you get there, if you find what you're looking for, there'll be a notebook. Record yourself in the notebook and I'll be out there to check who's done this and, and if your name's in there, I'll give you credit on this forum. And so this treasure hunt went viral, and lots of people all over the world thought it was a really cool idea to use this new GPS technology to create treasure hunts all over the world. So people started hiding not just treasure chests with notebooks, but all sorts of random things all over the world and then posting their coordinates online for people to find. This activity was given a name, Geocaching, and it's alive and well today, and it's streamlined on the official Geocaching app. But as geocaching has evolved over the years, so too has the level of difficulty at finding some of these caches. Sometimes it requires geocachers to climb mountains, other times it requires them to dive underwater. And in one case, Geocachers in the Czech Republic had to climb into this strictly off limits, five kilometer long underground tunnel where the only two entry points were on the two extreme ends. And to get to the geocache, you had to go to the middle of the tunnel. And of course, periodically this tunnel completely floods. On June 9, 2018, four geocachers in the Czech Republic decided, you know what, we're gonna go down into that tunnel and we're gonna get that geocache. So they made their way over to the Matalski Brook tunnel, which was one of the two entry points, and they climbed down inside. The reason this tunnel periodically floods is because rainwater gets dumped in there and, and the second entry point is literally sitting in a lake. There is literally water sitting right up against the lip of this entry point. So even light rain will get the lake to rise just enough to where all the lake water pours into this tunnel. And so the day these four geocachers are going into this tunnel, the weather forecast called for torrential downpours, flash flooding, and either these four geocachers were not paying attention to the weather or, or they somehow thought this wouldn't affect their ability to get this geocache. So these geocachers get down into the tunnel and they start making their way towards the center to collect their prize. When outside it starts pouring rain. It rained so much so fast that the lake entrance started dumping tens of thousands of gallons of water in on one side. And then on the other side, where this other entrance was at the bottom of a hill, you had all this water rushing in. So it was like two huge waves of water crashing in on them. And in fact, the survivors would say, because they were right towards the middle of the tunnel, they heard what sounded like a car was getting closer and closer and closer. And that's when they realized it was two waves of water crashing in on them. In a panic, they turned and started running back towards the entrance they came in on. But as they're running, they're hit with this wave. And two of the geocachers got sucked underneath, the other two were pushed up and were basically body surfing their way towards the lake entrance. And so as they're moving forward, the wave from the lake comes in and hits them. And now the water is dangerously close to the ceiling. And the two that have been pushed towards the lake entrance, they don't know what's happened to the other two, but they're just swimming as fast as they can towards the lake entrance. And they swam almost 2km in this tunnel. As the water got higher and higher and higher and they're barely able to breathe by the end. They only had about a couple inches of clearance by the time they got to the lake. They finally pop out and they get in the lake and then luckily there was someone that saw them and brought their boat over and picked them up. As for their two friends, unfortunately they didn't get out of there in time and they both drowned.