Although appearing natural and un-decaded, water logged wood quickly deteriorates. in order to stop this, the wood is currently being treated in tanks filled with a chemical called Polyethylene glycol. (PEG)
This gradually replaces the water in the wood and helps to protect it from decay and warping when it's dried.
The Timbers have been going through this process for several years now and at the end will go through a process of freeze drying.