A floating spa cover generally comprises an inflatable insulating and soar heating central portion surrounded by one or more independently inflatable adjustable rings. The inflatable central portion comprises a center section and a peripheral ring. The center section covers most of the spa water surface and includes an upper film of substantially transparent plastic and a lower film of translucent plastic separated by a gas-filled space. The first adjustable ring, connected to the central portion so as to be selectively removable, encompasses the central portion and is independently inflatable to selectively adjust the area of the cover over a first range of areas. The second adjustable ring, connected to the first adjustable ring so as to be selectively removable, encompasses the first adjustable ring and is independently inflatable to selectively adjust the area of the cover over a second range of areas.