"Too long" means, what, a month?
It depends. 0.4 pressure treated is good for submerged construction. 0.27 pressure treated will last a lot longer than untreated, and untreated would have to at least start the decomposition process to be beyond salvage. I don't have a time frame, I just don't know how long that takes, but I know that untreated cedar won't last one season underwater or uderground or against concrete.