The Portuguese man o' war isn't a jellyfish. It's a siphonophore, which means unlike a jellyfish, it's not a single organism. It's actually a colonial organism made up of many minute individual specialized organisms called zooids.
I guessed early on that you don't need to write 'war' in any of them. It meant I had plenty of time to watch to clock running down while not managing to get the last question...
Hm perhaps short enough for other quizzes, but I guess still too long for this one
Stinging marine species named after a ship? (or with a country in its name)
That would be short enough while still being accurate :) It would be nice to have them on the quiz. (better than having them somewhere else haha)