Effects of more than 1 control sector?

Can the effects of more than one different control sector be applied to the same normal sector?

As an example, I am trying to make an FOF that is underwater. Therefore wouldn't the sector need a control sector to make it an FOF AND a control sector to make it be underwater? Is that possible?

I know I've seen FOFOF's (Floors over Floor-over-floors) and I would think that would be a similar situation. If each sector can have only one sector tag, how do you apply the effects of more than one?

Simple, just give both control sectors the same tag.

Oh, so then when I apply, for instance, sector tag 5 to a sector in the level, both of the two control sectors with that number on their activated linedef thing will put their effects into that sector?

If so, that's really cool.

Yes. When a target sector has a tag of 5, every single linedef with a tag of 5 will be applied to that sector at once.

Ok, I gave it a shot, and I have developed my most complex gimmick to date with it. (Well kinda)
Thanks guys.