story identification - Identify a near-future book with automated news filters and floating countries

I'm trying to track down a book I read at some point in the late '90s (or possibly the early 2000's). It's a near-future novel, but there's only two things I remember from it.

1) Global society and the Internet (it might have been BBS/email-style rather than web-style) had reached the point where most people had their filters set up so that they only saw things which supported the viewpoints they already held. The (A?) main character had deliberately configured her filter to occasionally present her with something new or conflicting, just so she didn't get locked into one viewpoint.

2) Due to sea-level rise, there was a floating nation in the Indian Ocean. I forget if it was literally made of rafts/scraps tied together, or (more likely) a collection of separate boats that stayed together. I also forget if it was formally a country or not, but it had a large population and was a significant factor in world politics.

Does this ring a bell for anyone?

Answer

I think this is Earth by David Brin.

The news filtering technology:

The problem usually wasn’t getting access to information. It was to stave off drowning in it. People bought personalized filter programs to skim a few droplets from that sea and keep the rest out. For some, subjective reality became the selected entertainments and special-interest zines passed through by those tailored shells. [...] To avoid such staleness, Jen had hired a famous rogue hacker, Sri Ramanujan, to design her own filter.

“Let’s see what happens to that list,” she said aloud, “when we use threshold seven, categories one through twenty.”

“And the surprise factor, Professor Wolling?”

Jen felt in a good mood. “Let’s go with twenty percent.”

That meant one in five files would pop up randomly, in defiance of her own parameters.

And the floating city in the Indian Ocean, the so-called "Sea State" populated largely by a melting pot of refugees:

Too many landlubbers seem to be heading off the standard shipping lanes—vacationers who seek out nature’s serenity, but in so doing bring to silent places the plague of their own voices. (And then there is that catastrophe the Sea State, perhaps better left unmentioned here, lest we despair entirely!) Even the southern Indian Ocean, Earth’s last frontier of solitude, trembles under the cacophony of our cursed ten billions and their machines.

[...]

At night it had been no more than a sprinkle of lights, rocking gently to rhythmic tides. By day, however, the barge-city came alive with noise and commerce. And rumors. It was said that no place, not even the Net, spread gossip as swiftly or erratically.

Crat had no way of picking up most of the hearsay, though. Unlike the working ships, where discipline required a common language, floating towns were a chaos of tongues and dialects, whispered, murmured, bellowed. All the sea towns were the same. Miniature babels, sprawled horizontally across the nervous ocean.