一帮老友驾驶一艘豪华游艇出海为好友庆生，酒足饭饱之后，大家开始一个个跳入海中游泳。患有恐水症的艾米（苏珊·梅·普拉特 Susan May Pratt 饰）被抛入海水之后引起一阵恐怖，大家想赶紧把她送回船上，可是这才发现居然没人记得放下梯子。船身太高，一伙人想尽办法都不能爬上船去。此时，留在船上的只有一个婴儿，蓝天碧海对于悬浮于海面的六个老友来说变成了绝境，死亡的阴影在满是恐慌的人们之间迅速蔓延。看着好友一个个死去，一息尚存的人们仍然在寻找着最后的生机。暮色将至，一场暴风雨即将来临，是否有人能够穿越死亡的阴霾爬上游艇，生与死的较量在茫茫海面悲情上演。Amy, her husband James and their baby Sarah travel to Mexico to sail in the yacht of their reckless friend Dan with their common friends Zach and Lauren and celebrate the thirtieth birthday of Zach. They are introduced to Dan's girlfriend Michelle and they drink and recall moments of their past while navigating. Miles away from the shore, Michelle suggest to stop the yacht and swim in the calm water. Amy stays in the boat since she has a childhood trauma with ocean and Dan stays with her. Later, the irresponsible Dan pushes Amy overboard, falling with her in a prank. Once in the water, the group realizes that Dan forgot to put the embarkation ladder and the freeboard makes impossible to climb to the main deck of the yacht. With the baby alone in the boat and stranded in the open sea, they panic and their desperation lead them to a tragic fight for survival.