I much prefer superglue for smaller frags, and yes it's the same stuff from the hardware store (get the gel kind, much easier to deal with than the runny stuff). Anything cyanoacrilyte (sp?) based (that's the active ingredient in super glue). I usually put a glob on the end of the frag, and then quickly dunk it in the water and place it where I want it in the rock. It will work underwater if you're quick, however it's more effective if you can take the rock out and let it dry for ~2-4 minutes before submerging the glue.