This is the Tubmarine, a wood-burning hot tub. According to the company, the tub takes less than two hours to heat up and comfortably seats four adults. It's built from sustainably-sourced Kebony timber, 80% recycled stainless steel, and outfitted with a Kirami wood-fired water heater from Finland. The starting price is £15,450.00 (US$20,070). If you prefer a classic 1970s style tub though, Kirami has those for sale at around $4,000.