Originally Posted by
mhespenheide
The link
bikemig gave above can make the circumference calculations that you might be looking for. I'm not 100% sure if that addresses "flotation".
Yes, it is definitely a vague term but it seems like a vague concept. Perhaps comfort is what we are looking for. Or, is it a visual thing? I like the look of wide tires on a road bike and wide 700c are more appealing than wide 650b.