Bottom line is that there are several factors that will affect how a piece of wood floats, and swims. The density spreadsheet is a good referance to use as a starting place. (Light wood versus heavier woods.) I have it in Excel and if anyone wants it PM me with an email address.
Sealing, moisture content, top coat, pit wood, heart wood, sap wood, combinations of each and even variation within a wood blank will affect how a plug swims. Two blanks of the same wood might swim different. Hence why every plug should be test swam before it's placed in the plug bag.
This plug making stuff is addictive, with a large learning curve. But I love it anyway..