I made the terrible mistake of dimly remembering that the Portuguese man-o-war is not a jellyfish so trying to find out what they actually *are*

Anyway turns out they are floating colonies of at least 4 specialised organisms and science doesn't actually know anything about the early stages of their development, and there's at least one bit on the sex module (which they have, and it fucking swims off) that science no idea what it does.