Happy World Ocean Day! You, land-dweller, have pitifully limited living space: The surface of the globe you ramble on is some 71 percent saltwater, and the depths plunge down as far as seven miles. These dark and deep blue seas and their myriad critters are in jeopardy from overfishing, polluted runoff, climate change, and other land-dweller faux pas. But don't despair, says marine activist David Helvarg: we could reverse those trends with a citizen-driven movement to protect the oceans -- a "seaweed revolution." Meanwhile, Mother Jones magazine invites you to take a virtual ocean voyage, from the waters off Guinea in West Africa -- where you'll chase "fish pirates," ahoy! -- to polar-bear territory in the Arctic Ocean and beyond. Hop aboard!