Soaking Tub

Has anyone built a wooden soaking tub? I’m itching to build one and am not a fan of the coopered style that is most common with vertical staves and thus am leaning towards an Ofuro, Japanese style tub, or something similar that resembles a bathtub with horizontal boards, a rectangular shape, and no tension rings….this link gives you an idea of what I’m after…http://www.bath-in-wood.com/

There are two approaches to this tub and I’m interested in feedback from anyone that’s attempted this. Either method will require strong joints to hold several thousand pounds of water pressure contained inside it, but the way in which you go about making those connections strong and watertight seems a bit different to me.

The first is to build one of a rot-resistant wood, 6/4 Port Orford cedar is my first choice, and leave it unfinished to allow it to swell and tighten the joints when exposed to water. Ideally the tub remains moist with some water in it to prevent it from shrinking again….This is not something I have much experience in, and would welcome any suggestions on ideal joinery methods….

The second is to use a strong hardwood and create tight fitting, strong joints, then seal the heck out of it with epoxy to prevent any moisture from getting in. I could probably handle the joinery on this, tongue and groove, or splines on the sides and perhaps some kind of dovetail for the ends? or lots of biscuits and glue? The finishing however would more closely approach some boat building techniques, which I don’t have experience with.

Look forward to any suggestions!