Unfortunately we don't really have enough deep freshwater to bury them in. Below the thermocline freshwater has little oxygen and logs can last till the turn to fossils.

With saltwater it's a bit trickier because it's decently oxygenated even to depth and there is a lot of life dedicated to breaking down wood in the ocean. If you can get it to sink into the muck it lasts a lot longer though.

Of course, ships sink all the time.