Daughter of Elysium

Daughter of Elysium is a 1993 novel by Joan Slonczewski.

"The ocean world a thousand years later produced Daughter of Elysium -- floating cities of 'immortals,' whose machines keep them forever young. But what if the machines wake up, and demand 'human rights'?" (from Slonczewski's web page)

In the same universe as A Door Into Ocean.