There is no official Stranded II multiplayer mode. It just does not exist and it never will. It was planned to make one in the beginning of the development of Stranded II but the idea has been discarded.
The mysterious Multiplayer Button
You can enable a multiplayer button in the official Stranded II release and there are some PARTS of a multiplayer mode, but it is NOT WORKING. Click "More" to see how you can enable the WORTHLESS multiplayer button:
Fan Made Multiplayer Modification
Some users developed a Stranded II Mod with multiplayer functions. It's currently the only way to play Stranded II with more than one player.
Thread: http://www.unrealsoftware.de/forum_posts.php?post=157264&start=0
Webpage: http://www.oraclefile.com
Users (main developers of the mod):
The Oracle File
RoyalFlash
Note that this mod may still have many bugs and that it is not finished yet.
How to find people that play Stranded II Multiplayer?!
do NOT create a new thread for this! It will be closed/deleted!
If you have Hamachi ( www.hamachi.cc ) use the Stranded II Multiplayer Hamachi Thread
otherwise please use instant messengers or chatrooms to find people to play with! (the forum is not the right place for that!) you can also try the official Unreal Software IRC chat: irc://quakenet.org/unrealsoftware.de