Jellyfish women grow from the head down. These creatures begin life as regular jellyfish, with eggs growing into larvae that swim about for a bit and eventually find something to attach themselves to. They feed and grow as anonymous looking tentacled things. These eventually tuck their tentacles in and become small sea creatures. Feeding continues. Feeding and growing. So much feeding. Eventually the jellyfish bell and tentacles start to develop. And sometimes, the bell has a face.
Why certain jellyfish develop human-seeming faces is a bit of a mystery. If the jellyfish survives, it will continue to feed and grow – specifically growing downwards until it takes the form of an adult human female – often wearing a large and elaborate dress. This is clearly because the jellyfish woman incorporates the bell tent of the regular jellyfish form. It may just be an uneasy coincidence that this form exists.
When the jellyfish woman has feet, she finds a location where the depth is just right, and attaches herself to the sea floor again. Once this has been achieved, a jellyfish woman can in theory live forever. The sea depth is vitally important – no more than the head and shoulders of the jellyfish woman should be exposed by low tide. However, it is vital that the head at least is exposed as this is key to how the adult jellyfish woman feeds.
The ability of jellyfish women to learn and deploy human speech is another of their many mysteries. It is theorised that they are psychic and either draw the language from the head of a potential victim in order to speak, or project their words into the human mind.
The jellyfish woman will use either seduction to lure a victim, or will try to persuade them that she is a normal human at risk of drowning. Once the victim enters the water, the jellyfish woman uses the poison in her tentacles to further entrap her prey. She consumes small amount of blood, but her poison is addictive and causes victims to voluntarily return, craving fresh hits. Feeding over an extended period, coupled with the impact of the poison, will kill the victim.