Out of the safe, in trash bags pointing up and open is silly.
The water will go higher, get into the bag.
Anything the current or other floating objects doesnt knock over, will be moved by the two footed visitors.
Houses and anything that you think is strong enough, high enough, heavy enough, or there wont be strong current, is false hope.
"Its never flooded here....." Maybe not. Maybe you just havent seen it.
Buried or underground locations may stay there. Or the dirt may get waterlogged and your stuff along with several city blocks may float and wash away.
Anything you take to save can be stolen, confiscated, or damaged. Insurance may or may not pay.
Those who prep and pay attention usually have a better chance. There is still Mr Bean dumb luck.
I have seen plenty that has happened in person and some from news internet etc.
The concrete retaining walls on a local freeway, crossed the freeway.
Something can happen anywhere. Wiley Coyote proved that getting an anvil on his head in the middle of nowhere, and that cute blonde got killed by a falling toilet seat on her lunch break.
Fiction, yes. But goofier stuff has happened.
I have had fire arms in the attic before due to circumstances at the time. Rising water, storm surge and petty theft wasnt an issue. But storm damage, leaks, tornados, determined thieves (or some that just had more time ) and fire was a concern.
Water proofing:
Good ammo cans will work. Pistols, AR lowers, and some of the shorter uppers will fit depending on the can.
pvc pipe with capped ends can work depending on size of your pipe and guns.
Trash bags and ziplok bags, sorta but not for long.
I have also used a vacum sealer food storage by the roll. ARs will fit broken down, unpinned and seperated with a wally world sealer. Commercial sealers can do larger bags.
Some gun parts will poke holes in the vacum bags, so it doesnt work well with all of them.
ARs take up less space if un pinned and uppers and lowers toted seperately. This way they also look less like " he's got guns ".
When I " lived " in a hotel for work, I moved and stored mine in something other than gun cases. Boxes marked for something else, sport cases, tool boxes etc. If you look around a bit you can find stuff that will fit what you need to carry. This may lower theft a bit if the only target is firearms, but milwaukee, snap on, nike etc. will still be a tasty treat with a surprise inside for most thieves.
But it will keep you off the radar of most gun un-friendly types.
I also had a deer cam in the room. Thankfully all the footage was boring.
I'm no expert, but I've learned a few things. Some from success. Some from others. Some from mistakes. ( ok, a lot from mistakes )
Sorry for being long winded, but hope this helps ( or entertains ) some.