Don't worry about a cache, get yourself out of harms way.
I have a cache along the Susqehanna river that survived nearly 40 feet of water.Box Of Blues
As long as it's a good amo can and its snug in it's hiding place the worst that will happen wil be you digging it out.
Wow. That's pretty impressive! What did the log look like?
Log looked fine when I was there, and I know another cacher who was there maybe two weeks ago (don't know if they logged it yet) and said everything was fine.