Tim Samuel, an Australian photographer, took a rarely seen photo of a fish swimming inside a jellyfish. At first sight, it seems that the fish is trapped inside the jellyfish. National Geographic asked a couple of experts to comment on this phenomenon and they theorized that many types of animals associate with jellies, with the jellies providing some kind of ecosystem services that benefits the fish.
So, it looks like this could be just a “normal” day for this fish to use a jellyfish for locomotion (and perhaps also for protection and feeding). In fact, another photographer, Brent Collins, sent in a video (scroll down to view) that seems to show just such a behavior.
Another photographer, Brent Collins, has a video that shows such a fish “exit the Jellyfish, swim back inside the Jellyfish, and apparently steer the Jellyfish at will.”