It depends on the nature of the wood, and upon how it will be used. For instance, a cutting board has to take repeated impact from sharp objects, so you would be better off with an oil finish. A filmy finish like wax or shellac will be more likely to crack or break.
Wood can be used in bathroom or showers as long as sealers applied to it is maintained. If wood is taken care of, it will last a long time.
One of the best wood for bathrooms showers is teak. Teak is one of the few hardwoods that can withstand damp circumstances due to its low shrinkage in changing weather and great resistance to rot,...