John John Florence has surfed some of the heaviest waves on the planet. So has his brother Nathan. Which makes it especially telling when John describes a wave as “definitely one of the scarier waves we’ve ever seen.” See below. The Florence brothers recently chased what might be one of surfing’s most mutant slabs: a secret, below-sea-level reef somewhere in the Pacific, where thick ocean swells suddenly disappear into a horrifying ledge before detonating over almost no water. John had history with the place. “I had surfed this wave once before,” he wrote. “Nathan had never been and really wanted to see it.” They almost didn’t go. “We were keeping an eye on a swell that popped up and debated going until the very last minute,” John explained. Eventually, curiosity won.…