I've decided to go with the Captain instead. Was I supposed to do this, or should I have gone to the Underdark? Can I still go to the Underdark?

No, you've done the right thing. By going with Saemon, you'll get access to a map that you can't otherwise reach, and after you've done the quests there you can still enter the Underdark.

SPOILER
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Siding with Havarian was the best thing to do!You shall gain access to the Sahuagin city and from there to the underdark.Should you have gone just to the underdark you would have lost a fun and rewarding part of the game.
You were faster J'aran!!!!

[ 01-25-2002: Message edited by: Helspanth ]

[ 01-25-2002: Message edited by: Helspanth ]</p>

Yeah. You can go either way. All you would miss would be a strange Spectator Beholder and a nice spear. Thats its. Oh and a piece of the silver sword.

<blockquote>quote:</font><hr> Yeah. You can go either way. All you would miss would be a strange Spectator Beholder and a nice spear. Thats its. Oh and a piece of the silver sword. <hr></blockquote>

In my opinion, the spectator beholder is worth the trip in itself. Hes very entertainig, however, by neglecting this part of the game you also lose the all important super groovey(spoiler)...
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Cloak of Mirrors! The item that renders all beholders as non-factors. Just equip your best fighter with this thing, send him by himself into a room filled with the eye tyrants, and hack away with impunity...or just stand there and let the beholders take themselves out. Its a very handy item, as it reflects any directly targeted offensive magic back on the caster. The description says it only works on damaging inflicting offensive spells, but Ive seen beholders petrify themselves against it. Not to be missed.

Chev