Water Corrosion in HID headlamp

A couple weeks ago, there was a bad flood. The next day my middle beam did not work, but the high beam does. I took it into repair, and they said it was from corrosion and the computer for the HID doesnt work. I tried to get my car insurance to pay for it, but they said it was a maintenance issue. I never had this problem with rain before now all of a sudden a flood around 1 foot deep, and it doesnt work. The cost is very expensive so my questions, do they need to replace the whole front headlights costing around 1k each, or can they just replace the computer control?
Please help as Im desperate to know and learn how to avoid this again.