When Greg Heffley and his family hit the road for a cross-country camping trip, they're ready for the adventure of a lifetime. But their plans hit a major snag, and they find themselves stranded at an RV park that's not exactly a summertime paradise. Things only get worse for the Heffleys when the skies open up and the water starts to rise, making them wonder if they can save their vacation—or if they're already in too deep.