Acrylic hydromassage bathtubs fall in between cast iron and fiberglass tubs in terms of price and benefits. The chemical compound acrylic is waterproof, lightweight and durable, making it ideal for making bathtubs. Tubs made from this strong and light material are a lot easier to work with than cast iron and steel bath-tubs, which chip easily and are excessively heavy in larger sizes, like whirlpool bathtubs.