World War Z - Max Brooks

If you still are not convinced about the very real dangers of zombies out there, I would strongly encourage you read World War Z - an oral history of the zombie war. Albeit a fictional account of the worse case "what if" zombie scenario", its very real description of the possible menace these monsters pose is all too chilling.

The story recounts how the zombine virus (Solanum) infects a rural area of China. With the authorities unaware of the dangers the virus posed, the plague is allowed to sweep across the country and into the western hemisphere through the illegal organ black market. From here mass chaos ensuses as the Great Panic hits Europe, North America, the Middle East, South America and Japan - indeed, no one is safe as all parts of the world are affected. Some countries respond by closing their border, while others have no response but to run and hide. Other than the truly rich, some of whom are smart enough to escape to Antartica or floating sea barges, zombies take over every square inch of the globe (including the sea floor!)

Many infected refugees had tried to swim for the ships and then reanimated after they drowned. It was low tide, just deep enough for a man to drown, but shallow enough for a standing ghoul to reach up for prey. You saw many swimmers suddenly vanish below the surface, or boats capsize with their passengers dragged under.