There was a large POW camp in Papago Park during WWII. One subset of the prisoners were commanders and crew from U-boats. They wanted to escape, to Mexico, where they thought there would be people sympathetic to their plight.
They started to dig a tunnel. They told the guards a story -- that they were making volleyball courts. And they had a stroke of luck -- they had obtained a map. There was a river on the map -- the Salt River -- which led into the Gila River, which fed into the Colorado. They could take this route, if they built a boat, all the way to Mexico. They wouldn't have to hump the distance by foot!
So, they also built the pieces of a boat. And late on the night before Christmas Eve, the other prisoners celebrated with loud singing and merry-making to cover the fact that a large number -- somewhere between 25 and 40 -- of men were escaping from the camp through the tunnel to hike to the Salt River to assemble the pieces of the boat and begin their journey to the border.
If you know anything about the Phoenix area in the winter, though, you might have an inkling at what happened next. The Germans escaped and made it to the Salt River, only to find that it was dry. That was a blow, but they pushed on to the Gila. Which was mostly dry -- just some puddles. On the morning of Christmas Eve, the Germans were facing cold and the only water was drizzling rain.
Meanwhile, back at the camp, their escape had gone unnoticed until the first of the Germans walked back to Phoenix and started to turn themselves in. A few holed up in caves and other outcroppings for a few days, but the official story is that all of them were eventually rounded up and ensconced safely back in the POW camp.
It's like Hogan's Heroes in reverse!