O2 Sensors underwater - will it spit the dummy?

We're running a stock GTO LS1 with a Speartech loom & PCM, retaining the two lambda sensors on the downpipes. However, for a fair portion of its life the O2 sensors are going to be underwater or covered in mud. That means they'll either cool down too much to give a useful reading, or die and give no reading or a bad reading.

Obviously we don't want the thing to into full-on limp-home mode, and running open-loop all the time would probably kill the mileage. Can anyone tell us what the PCM will do if it sees bad signals from the O2 sensors? Any info on just how limp the limp-home mode is?

Cheers!

if you had the ve table worked there's no reason your mileage should be that bad running OL.