As the urban legend says, there's a visible line where the Pacific and Atlantic oceans meet, between two coloured bodies of water. You could be forgiven for assuming that the sea had been deliberately dyed on each side, however, this is not the case. The contrast is due to differences in the mineral and chemical composition of the masses of water, and different surface and deep-water currents. Actually, that place is the Gulf of Alaska, there's only the Pacific ocean, and the sediments come from glaciers.