So, I havent had time to test it myself. But if a body is wearing heavy armor.. And you throw him in a river, will he sink or merrily drift down the river?

Float.

You would think considering they're wearing armor that weighs 20lbs they'd sink. Ahh well, maybe I'm picky

Well we swim like a fish while wearing it so it doesn't surprise me that bodies with it on float.

Haha true

I wasted spent 20 instructive minutes trying to get a body to go over a waterfall--the one near Valkreath Tower just east of Whiterun. Stupid bandit kept floating to shore instead. I guess they won't float out of a cell.

And the thieves in leather armor I throw into the Riften canol always sink like rocks and are never seen again. I suspect it's something in the water....

It might be because a lot of the rivers and
streams flow sideways.. Happens to me alot

In Skyrim, the standard for smithing armor was set by the ancient Nord, Nike, who used a classic method called "Nike Air" where small pockets of air were encapsulated within the steel (or whatever material), and, as you know, enough trapped air will make anything float on water. This was done to provide comfort to the most discerning Nord warrior. Once NNFTA (Northern Nord Free Trade Agreement) was passed and the TTO (Tamriel Trade Organization) came into existence, the Nords of Skyrim were able to outsource production of 'Nike Air' armor to countries that allowed slave labor (such as, Vvardenfell). Thus, 'Nike Air', once a luxury, became the standard. After the eruption of Red Mountain, aquiring cheap 'Nike Air' armor was no longer possible. However, Nords would settle for nothing less and Nordic weaponsmiths were forced to create armor of this quality while receiving less payment for it. This explains the crappy dispositon of most weaponsmiths in Skyrim.

Interesting, I was able to do it.

Sounds like a good explanation to me.