Shipwrecks, sunken treasure and lots & lots of money: To help mark World Oceans Day, here are 7 amazing facts you probably didn't know about the deep blue sea. #WorldOceansDay RELATED BTN STORY Deep Sea Exploration www.abc.net.au/btn/story/s4530706.htm Law of the Sea www.abc.net.au/btn/story/s3970036.htm Microplastic Ocean www.abc.net.au/btn/story/s4425888.htm