I've come up with a race of intelligent jellyfish-like people called the tentacua who live in the deep ocean, and I'm trying to figure out a plot to use for them.

Details:

1. They are about eight to nine feet tall at their adult stage. Their reproduction cycle more closely resembles that of a jellyfish than a humanoid, except that they have three genders instead of two.
2. They have a crown on their head that looks like a jellyfish body. The front of the crown is studded with bioluminescent tissue, which they flash in different colors and patterns to communicate. Their language is quite sophisticated, about on par with human languages, but has no vocal or gestural components. (The name "tentacua" is simply what we would call them.)
3. They live in villages and get food by hunting and farming. The closest analogue to their level of societal sophistication would be human settlements just before the Dawn of Civilization.
4. They are the only intelligent life native to their planet, whose surface is about 90% ocean. Their closest neighbor planet hosts an advanced intelligence capable of high-speed interstellar travel.

Can you guys think of a story I could write about this race? I mainly do short stories, but I'd be willing to tackle something closer to novel-length if the idea intrigues me enough.

EDIT: I found a way for them to have a writing system! Fluorite glows when exposed to ultraviolet light, which the tentacua can emit from their crowns. The tentacua could write by etching symbols into a stone which is made of fluorite covered by a thin layer of some other mineral; scratching the outer mineral away would expose the fluorite, like scratching a design into a scratchboard!