Usually this corrosion and shorting happens on the 12V side, same as any gas car. Those catch fire occasionally after flooding in salt water just the same. The high voltage battery is sealed.

The saltwater flooding threat is absurdly but predictably exaggerated. Teslas are renowned for their ability to be driven through flooded roads - 2 to 3 feet of water(video link).  Saltwater?  Solution:  take the EV or any vehicle for a full-blown carwash and hose-down after an extremely rare seawater flooding event like this hurricane.
Watch;  "Tesla Model 3 Conquers Deep Floodwaters - One Of The Safest Cars In The World!" :
youtu.be/j_mMtDjjvK4
  Also see these articles offering an informed contrary perspective re EVs, floods, risk, damage etc:
1) insideevs.com/news/521633/tesla-model3-handles-deep-flood/
2) auto.howstuffworks.com/fuel-efficiency/vehicles/electric-car-shock.htm
Oh yeah - and when, like Floridians, you've had ample warnings that another major storm is about to assault or asSALT  you - take intelligent pre-emptive precautions - not just with respect to any vehicles you may own. It ain't rocket or socket science!
PS. add "h..p // ww" etc to my above links to get them to work - this site doesn't like/allow external links.
Paul G