TexasCHLforum.com

I am going through a "safe search" myself.

This is the best advice written down that I have run across. Get a beverage, takes awhile to go through it: http://gunsafereviewsguy.com/

One of the main points, if you haven't already run across it, is that nearly all "gun safes" are not safes at all, they are at best fancy Residential Security Containers, i.e. metal boxes of varying thicknesses that can be opened with pry bars in minutes, in most cases. Fancy expensive ones have safe-like features, i.e. lots of visible locking bolts and multiprong handles, but the actual construction of the box and the (hidden) linkage are often flimsy.

I am following his advice of getting the least expensive RSC I can, basically a couple of stack-on or homak-type boxes, hiding them and making them as difficult to find and work on as possible, and saving up for a real safe, i.e. buying a used TL-15 or TL-30, or a new/used Sturdy Safe. I have been perusing ebay and note that if you watch for awhile you can usually come up with a TL-15 or TL-30 for what many of higher-priced "gun safes" in a gun store or big box store go for.

If by "waterproof" you mean safe from flooding, I have only seen one or two safes advertised as waterproof, and I think they were oriented to water from firefighting actions in fire, not flooding. Best defense against flooding is probably put safe above ground level. Or move.