Oak isn't good with moisture as far as I can tell, (I worked as a sawyer on a Wood-Mizer mill at one time and you never forget the smell of sour oak),. Redwood and Cedar aren't very dense so would absorb a lot of the moisture, which could cause problems.
I think I would look at pecan, hickory, maple or another dense wood. Where are you and what is locally available to you that might work well?
Ditto what Dallas said. Redwood, cedar and oak would not be my first choices and would be on the bottom of my list. I would use a hard maple, cherry, pecan, hickory, etc. Any good dense wood would work. I would finish it with polmerized tung oil. It is water resistant and then you could just wipe up the moisture that would acquire inside.
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