The first time Sarah tries drugs is the first time she goes out with Tim, who was a customer of hers in the Dew Drop Inn Cafe. Tom is sweet and cool and after one night, she moves in with him| leaving behind her alcoholic mother and younger sister, Karen. For a while life is great and drugs are just part of the deal and most of the fun. But then things start getting complicated...。Lisa和Kate两姐妹在墨西哥海岸度假,她们在海底观鲨铁笼中潜水观赏鲨鱼时,牵连铁笼的绳子突然断裂,观鲨笼掉落到47米深的海底。由于所存氧气不多,她们只有一个小时的时间逃脱牢笼回到水面。而此时,大白鲨也在她们周围游弋着。47米深的海底一片漆黑,只能通过手电筒观察铁笼外面的情况。水面上工作人员的声音时有时无,救援队也迟迟不见踪影,姐妹俩都非常害怕。面对仅剩的氧气,她们必须马上做出选择才有一线生机。为了避开鲨鱼活着游出水面,姐妹两人与鲨鱼之间展开了一场斗智斗勇扣人心弦的生死较量。。