We’ve seen surfers ride standing river waves. We’ve seen bodyboarders huck themselves down dam spillways. Jamie O’Brien has built practically an entire career around Jackass -inspired aquatic hijinks, from his early days on YouTube surfing Oahu spillways. But this? Absolutely not. Footage from Pakistan’s colossal Tarbela Dam shows its spillway gates opening and an almost unfathomable amount of water roaring downhill. When the torrent reaches a hydraulic structure near the bottom, it rears upward into what looks like a gigantic standing wave. The scale is difficult to comprehend. Tarbela sits on the Indus River northwest of Islamabad and ranks among the world’s largest earth-and-rock-fill dams. It stands roughly 147 meters—or 482 feet—above the riverbed, while the dam itself contains approximately 142 million cubic meters of material. And Tarbela can move some serious water.…