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 a campsite 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.