“More than 5 trillion plastic pieces, with a combined mass of more than 250,000 tonnes, are floating in the ocean. … Large items such as bottles, buoys and plastic bags would be expected to degrade into smaller and smaller pieces of floating trash. So where is all the microplastic? … Polymer chemists say that all the plastic we have ever made is still with us.” (http://www.nature.com/news/fate-of-ocean-plastic-remains-a-mystery-1.16508)
Obviously, pollution-evolved creatures of the depths are constructing Lego-like weapons of mass destruction.