Originally posted by Andy
Steel boats float (snip)
Actually, if you want to be technical about it, it's air that floats (in water). In the normal case, the hull serves to contain the air.
Fill a perfectly airtight hull with a substance greater than or equal to the density of water and see what happens.
A trivial example is to consider what would happen if you filled the hull with lead.
What does that have to do with the current thread? Weeeeelllll, maybe there's a metaphor in there somewhere.