Crimeny Jordan, now I'm confused.
They don't teach you the glass and gravel theory in Boat Design 101? ;-)
Sometimes the easiest concepts are the very hardest to explain.
I explain complex concepts, which are often virtual in nature, to clients all the time. They can't see it, feel it, smell it, taste it or touch it so grasping the concept is difficult. I've found that by explaining the concept from as many angles as I can often works; Eventually one method is able to be visualized and *click* they get it.
I am sure that is the case here. I'm sure squidd just had a 'moment' and the light bulb will go on.
I agree with Minnewaska that the confusion is the difference between being buoyant and not being buoyant. I attempted to explain that through an alternative method which may or may not help with the *click* moment.
Seriously, if you think I'm off my rocker, try using my little gravel experiment with a student that has never learned physics; two equal cylinders, add gravel to one, demonstrate that they both still float ('positively buoyant', just for Minnewaska), but point out how much lower the heavy glass sits in the water. Voila, the student will understand the difference how two boats of the same dimension will still float.
My other attempt at explaining this would be on a whiteboard. Some people learn better visually.
Now lets stop beating up squidd. I'm sure it was just a minor moment and now that he's slept on it will understand.