The following is directly quoted from SBL's Website.
"Will water hurt it? Saltwater?
Our leather laughs at water. The leather is tanned with oil and therefore repels water after a few hours or even a few minutes. The tobacco and black leathers are 100% waterproof like quality hiking boot leather is. Your leather will be fine if it gets rained on and there won't be spots afterwards.
If you fall in the ocean with it, then soak it in freshwater for 24 hours. Change the water about 12 hours into it. That's what I did when I took my bag shark diving with me for pictures. I now use it as my diaper bag. If you only get a little salt on it, then clean it off with water and then oil it. The rivets corrode though."