Exterior masonry of any kind should not continue from outside into the enclosed inside portion of the house; there should be a break containing flashing and/or waterproofing. If such a barrier has been omitted, it will most likely have to be installed. Sealant or caulking is only a temporary repair at best. There is no way to know how to solve your specific problem without seeing a detail of the indoor/outdoor condition. If there is water in contact with solid masonry or a crack it will move through it by gravity, hydrostatic pressure, or capillary action (wicking) but in a properly constructed slab, a layer of coarse gravel or crushed stone (not fine materials like sand or clay) prevents water from being wicked up to the bottom of the slab (unless there is hydrostatic pressure present). Water vapor moves through a material if the air above the slab is drier. In a properly designed slab a sheet vapor retarder is sufficient to prevent water vapor from passing through the slab. In the case of hydrostatic pressure a waterproofing layer is required below the slab. None of this is difficult; it's standard concrete construction practice in commercial construction but it appears to be often ignored by home builders.

I ripped up the carpet in my bathroom today with dreams and ideas in my head of my complete bathroom makeover. What I want to try is a hardwood-look technique on the bare concrete. I plan on using a wood grain rocker tool to use for the texture, but I have no idea what I should cover the floor with. Would a concrete stain (gel stain?) be appropriate? Would it be best to stain the entire floor a base color, and then use the rocker with a darker color stain? Guess I don't really understand stains too much, so thanks for your help!

And the type of subfloor you are sitting on. Adding poured concrete onto a wooden subfloor isn't a lot of fun. And then you get to discover the joys of etching and staining that occurs with concrete. It is as bad as MARBLE. Personally I would look for a HIGH END porcelain tile ($10 - $15/sf) to get the look you want. Porcelain will not have the staining/etching/MAINTENANCE issues like concrete. Yes. Concrete has maintenance = same amount of money/time/effort as marble.

You can - it's tricky to do well a the time of the flooring pour, and you'll still need a "pan" and waterproofing under the shower portion of the floor. We had to rig up a form that left a 1.5" shower side depression in the floor, waterproof it and then create a custom sloped shower. We used forms because we were not doing concrete, but even if we did concrete after that - it would not have been seamless to the floor. Can be done - takes a ton of skill and planning.