Nonea
You're right - underwater play is just too hard to implement. I can't see it working at all without a rewrite and that's not going to happen.An underwater area that you can swim down into (thinking how WoW does it) wouldn't work without completely re-writing the engine. The engine is 2D, so you can't jump and you can't swim on more than one level of water at the same place (or can you? Though it'd probably be restricted to set levels like running over the canal to the Kitin Jungle in Silan). Even more, monsters won't target you while you're swimming (I don't know how hard this would be to change).
A Waterworld Region (no land at all), though tempting, is almost as unworkable:
- would require boats to be manned
- nothing that can sink is retrievable
- you fall in, you swim, but a long time in the water (Atys weeks, months) is stretching credibility
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It's bad luck to be superstitious . . .Palta e decata, nan nec ilne matala.
When one goes on a journey it is not the scenery that changes, but the traveller