The following is from Diamond Spas, it is a copper whirlpool tub:
There are many of these curved free-standing tubs with very graceful lines. This one is from Kohler:
Here is a little blurb from Kohler about the material in the free standing tub:
“This is the shape of things to come. The Lithocast line of freestanding baths introduces a premium solid-surface material that allows for new geometries, textures and designs for the modern bath. Lithocast offers the beauty of real stone yet is warm and comfortable against the body. And it’s easy to clean (always my favorite).”
The incredible variety of shapes, materials and styles for bathtubs is amazing. Before making a decision on your bathroom makeover, think about installing one of the non-traditional style tubs!