Tim Samuel, a self-described "ocean obsessed... lover of photography and adventures," captured the image off Pass Beach in Byron Bay, Australia.
"There were no other fish in sight," he told CNN by phone. "I just stumbled upon it."
'Let nature take its course'
"(The fish) seemed to be struggling a little bit, as it would swim around, it would try to swim in a straight line but the jellyfish would knock it off course, would send it in little circles or loops.
"It was a tough decision, I definitely thought about setting it free, but in the end decided to just let nature run its course."Â
Much of Byron Bay, where Samuel is based, is a designated marine park and is protected from fishing. As a result, Samuel says, marine life is thriving.
He says he's been in touch with marine biologists through the nature publication Australian Geographic, who "say they've never seen anything like it.
"At the time knew I'd stumbled upon something pretty special."
"It's difficult to tell whether disaster has just struck, or whether the fish is happy to be in there," he is quoted as saying.
"Although by the photographer's description of the fish swimming, my guess is that it is probably quite happy to be protected in there"