What about when you go down very deep in the ocean. There should be darkness and in that darkness should have sea creatures that emit light. Like jellyfish or glow creatures.
Jellyfish sound very nice, especially at lower sea levels.
Even though the sea is rather boring, such variety at low levels would be cool enough to make me give my support to this suggestion.
We're doing a mod project, check it out:
That would be really awesome
Dungeons to Monster Shelters
Discuss Woodland Mansion Transformations
It would make the seas easier to navigate so I support.