Thank you, Guy
Let me start with Tom and decay and 100% moisture. Like when a ship goes down that was carrying a load of cargo, like the old wooden ships, the Spansh Galleons downed in Florida waters (???? hurricanes!) No remants of the ship, but we'll attribite that to its parts floating away. What about the treasure chest? Why when Mel the treasure hunter guy found the mother lode from the Atocha, was it all in a pile on the ocean floor? Where was the chest? Wood does not last very long in warm, shallow marine waters, but that's another story.
Why are boats primarily made out of material other than wood? Hmmm just a question to ponder.
But on to Tom's question about underwater logging? Well, I see logs and other tree parts in streams and rivers and they decompose.... oh but you're talking about ships carrying logs that spilled their cargo, or went down. You will not get decomposition for a number of reasons. Foremost, deep down underwater there's this thing called hydrostatic pressure, where the pressure gets huge the deeper you go. Fungus simply has not evolved under conditions anything like this. The pressure alone will kill it.
How much sunlight is there, down deep? There's a myth that mushrooms grow in total darkness, which is both a wive's tale and false, with exceptions in the lower fungi (yeast, molds, etc). Higher fungi (produces mushrooms, or fruiting bodies) have evolved over billions of years with this really regular diurnal rhythm of nighttime-daytime. This, as far as I know, has been rather constant, for the last billion or two years and the fungi have evolved under those condition, not underwater where beyond 50 meters deep, sunlight, for all practical purposes is nonexistant. Mycelium can grow in the dark, but to complete the reproductive cycle, light is a must.
Temperature. How warm do you think it is a meter off the bottom of Lake Superior, or any freshwater lake or saltwater body? Probably cold. Fungi, in their normal environment, have evolved with varying temperatures. They depend on those fluctuations for their development, partly the reason you see mushrooms pop up overnight (cooler temps) or some that fruit only in the Fall (cool snap, after the Summer heat). Mushrooms, with few exceptions (notably Enoki, (Flammulina velitipes)) do not thrive in the cold, cold conditions. It takes a warming up for the dormant mycelium to revive and continue the decay process. On the bottom of a highly pressurized, dark, submarine world, the temperature does not fluctuate much. It's like a perpetual refrigerator.
So, there's no need to go into the fact that actual reproductive fruit bodies (the mushrooms themselves) can not develop and cast spores deep down underwater, pretty much bringing reproduction to a grinding halt. I doubt, also, that there's abundant oxygen down deep, but I only know certain things about the deep marine environment, and how much or little oxygen there is, is only a guess. I will leave the topic of oxygen for another post.
Any questions so far as to why one can say "100% moisture will prevent decay" and how they could substantiate their point and actually be right? OK, lets move into a land-based environment in conditions that are more realistic to what we're working with.
