Like Karritz I mostly don't bother with dive lots.
I don't think you're missing out on much, but that is just my opinion. I never use dive lots, and if I download a world that has them, I delete them. As far as I know, apart from the dive skill, which doesn't seem to do a great deal beyond your sim finding random little collectibles, and map pieces to hidden islands which only works in Isla Paradiso, it doesn't add a great deal to gameplay for me apart from just something different to do once in while ( that I don't bother with anyway :D )