Does a DemerBox float?

Yes, it does, as long as the Port Plug is properly inserted and tightened in the port hole (outside the box, not inside) and the lid gasket is clean and the box is latched properly.

The DemerBox lid stores all of the components like the battery, speakers, and circuitry - making the unit top-heavy.  

To get the DemerBox floating upright, load a couple items into the storage compartment. This will act like a counterweight.