This article examines why nutrient pollution emerges as one of the greatest threats to water quality. Using examples such as in the Chesapeake Bay, where large schools of jellyfish scare away swimmers. In the Gulf of Mexico, a 3,000 square mile "dead zone"" threatens a multi-billion dollar fishing industry. In Qindao, Beijing Olympics officials had to scoop large masses of green algae out of the water before sailing races could take place. These are all effects of eutrophication- pollution caused when nitrogen, phosphorus and other nutrients enter the water in massive amounts. And it's a problem with which people in both the developed and developing world are becoming frighteningly familiar.