Wait till the water level is high enough to cover then damage then sell!!!! Seriously, this reminds me of one of my corrals that was built out of used oilfield pipe. It has rusted from the inside out and the oil field guys tell me it had acid in it when it was taken out of oilfield service and that is why it has rusted/rotted away so bad.
I would check with the dock repair services near you. I'm sure yours is not the only one in this shape and perhaps they could direct you to a repair they have done that you could look at. The time to fix it is certainly NOW while the water is low!!!
CowMan
