When a team of five explorers embarked on a 1,200-mile journey down the Rio Grande, the river that marks the southern boundary of Texas and the US-Mexico border, their goal was to experience and capture on film the rugged landscapes of this vast frontier before the controversial construction of a border wall changed this part of the river forever.The crew—Texas filmmaker Ben Masters, Brazilian immigrant Filipe DeAndrade, Texas conservationist Jay Kleberg, wildlife biologist Heather...