Zombies...

why_ask_why said:
since they don't breathe there should be no oxygen in their lungs which makes them just as good as an anvil at floating

hmmm. They could walk the seafloor I suppose. You'd be like Kevin Costner in Waterworld, minus the gills.
 
why_ask_why said:
since they don't breathe there should be no oxygen in their lungs which makes them just as good as an anvil at floating


Decomposing tissue = buildup of gases in the diaphragm