 And it was high risk the whole time. But at the very end, they send five divers into a tube hundreds of feet below the ocean floor to remove heavy safety plugs. And the tunnel had no oxygen or light. And the narrowest part of it was only five feet in diameter. And the divers were to travel all the way to the far end of the 10 mile long tunnel. And then inside a series of pipes, there were only about 30 inches wide. So they became kind of smaller and smaller.