格雷一家人因房子损坏而蜗居在外婆家的地下室许久，他们绞尽脑汁策划了一场"穷游"——房车露营。露宿野外远没有想象中的简单，露营器材店的伙计甚至建议带上一些特殊的装备——驱逐熊的狼尿、防壁虱的驱虫水、急救箱、防水火柴、蛇咬疗伤包......这一趟荒野冒险之旅似乎惊险重重，格雷一家能平安度过吗？ 格雷一家继续着他们的野外露营旅行。房车营地里，格雷不慎结交了一大帮调皮捣蛋的新朋友，一场激烈的"水战"在所难免；格雷家人沉浸在泳池派对的狂欢中，但灾难悄然来临，突如其来的暴雨把他们困在房车营地里；更糟糕的是，营地警报拉响，道路桥梁坍塌，所有人陷入混乱......而水位还在不断上涨，他们将如何逃出生天，还是会越陷越深呢？

Greg Heffley and his family hit the road for a cross-country camping trip, ​ready for the adventure of a lifetime. But things take an unexpected turn, and they find themselves stranded at an RV park that's not exactly a summertime paradise. When the skies open up and the water starts to rise, the Heffleys wonder if they can save their vacation—or if they're already in too deep.