Isuzu D-Max 2013: Problem with waterlogged diff

I've had a number of problems with the 2013 Isuzu D-Max LS-M Auto Crew Cab I bought new. We've had a lot of water around my area in the last four months and my back diff got full of water and was a write off. The replacement cost was $3582. I asked about the front diff and the transfer case, but there was no water in them. You would think they would all have water in them. I think something failed.