Jellyfish Mix the Oceans
This video shows a luminescent dye being delivered into the path of a swimming jellyfish. As the jellyfish swims through the dye you will notice that it "carries" some of the dye along behind it. The dye is not actually carried, but "follows" the jellyfish as its forward movement causes a low-pressure area behind it that the dyed water moves in to equalise.
In this way it has been proposed that jellyfish contirbute significantly to the mixing of the oceans.