Don’t pee in the pool!

Absent any recent knowledge about chemistry, and also a pre-21st century mindset that the world was large, and that actions in 1 place don’t impact others, they dumped chemical weapons into the ocean.

http://www.treehugger.com/clean-water/65000-tonnes-nazi-chemical-weapons-were-dumped-baltic-sea-70-years-ago.html

Sadly this seems to still be common, albeit regulated practice: http://www.gc.noaa.gov/gcil_mp_ocean_dumping.html