This is a hot tub I built a few years ago it has three coiled copper pipes that start at the bottom of the hot tub and then span out into a spiral cylinder shape where the fire is then built and then the pipes go back into the upper part of the tub (works great) as the water get hotter it rises up the coils an shoots out from the pipes
The inside is white fiberglass plastic reinforced paneling and the outside is 1.5 inch water proofed pine with an insulated bottom will also include the lid and the stairs with built in towel/ robe holder this was a labor of love and could use a new home where it gets a bit more use
will just need the joints re calked after moving
And your good to go with a like new off grid fire powered hot tub / cold plunge.
Easily fit my wife myself and our 6 year old