I had not tried advanced rendering, but I know I will have to lower a few settings. I guess that's the price you play for installing a complex expansion like this on a primitve computer.
I will edit this post to report on the results later.
EDIT: It worked, I entered Rubelis's house and had him scuba dive and it brought me into the underwater world perfectly. I set all settings I did to low and turned on advanced rendering. Now I'll have to deal with Error 13 a lot more but hey, it's Under The Sea for me!