Water and burial both help to preserve a body. Sorry I hate talking about this as I'm sure you hate hearing about it.
I've studied water based decomposition for some time now as there are many different variables at hand with bodies found in water.
Bodies do not float to the top of a body of water until they have decomposed considerably. Bodies typically reemerge from the same area they were submerged and drifted down. The gases inside of the body cause it to raise to the surface of the water.
Now, what makes our stomach area bloat during decomp is is bacteria that builds up in our intestines during the purification process. If someone is in water that is running and filters to another waterway, their bowels can be flushed out, thus causing the purification process to be delayed since the bacteria is being washed from the body.
Masecation and marbling and skin slippage are typically what is most noticeable on a decomposed body coming from water. Bloating of the ocular regions and face typically occur due to cranial infection (the brain isn't necessarily being cleaned out, just digestive/respiratory/ reproductive regions)
There's so much more to this IMO. And bodies in water have much variation on how they putrefy and decompose according to the waterway they were disposed in.
Some people here might be versed in dried bodies, I'm versed in bodies pulled from water. To each his own. We all can add much here