Mossy wood

I saw there was a similar post, but looking at the new copper block I just thought it would be a nice idea to have a "mossy" wood. The woodblock which is placed in water would change its color first (like the real one) and after a very long time, it might also become "mossy" just like the sunken ships in real life. So just like placing a copper block and waiting for it to change color the wood placed in water would also change with time. To prevent your ships from getting mossy we would just use wax or sth. 

This would be also a nice addition to already exiting shipwrecks but what if we could add this kind of wood into some caves? Maybe "water" type with some wood inside, or underwater mineshaft.