The words spa, hot tub, and jacuzzi are often used interchangeably to describe a large tub of hot jetted water most often found outdoors. The key thing to pay attention to are the modifiers also being used to describe them. Words like “acrylic” or “in-ground” give you a clue to their construction. The term “hot tub” was first used to describe an outdoor wooden barrel filled with hot water. During the 1950s, the Jacuzzi brothers modified this concept by adding a hydrotherapy pump and jets for relaxation. The word “spa” comes from the thermal springs favored by the ancient Romans for medicinal purposes. In the present day, “spa” is also used to describe locations offering massages, steam baths, and mineral-rich spring water- and seawater-based health and beauty treatments.