"The fireweed began each spring as tufts of hairy growth and spread across the seafloor fast enough to cover a football field in an hour.

When fishermen touched it, their skin broke out in searing welts. Their lips blistered and peeled. Their eyes burned and swelled shut. Water that splashed from their nets spread the inflammation to their legs and torsos."

http://www.latimes.com/news/printedition/la-me-ocean30jul30,0,2100795.story?coll=la-home-headlines

All that from a little blue-green bacteria. Imagine that.

This is a long one but well worth the read.