Abstract: This invention is a “bubble glider” which is a modified hybrid of the hot-air balloon and the glider. It has a distinct undulating forward motion. A simple bubble glider has a soft air-bubble, a hard air-bubble and a thin body and is made of 0.25 mm PVC sheets. It is used inside a completely sealed water tank with an external control unit. An operator uses the control unit to vary the buoyancy of the soft air-bubble and completely control the motion of the bubble glider. Specifically, the glider can glide forward and backward, change direction, take off and land vertically, float motionless and so on. In generalization, bubble gliders can be of many shapes and sizes, and made of, practically, any material. They can be designed to operate in totally closed containers or in open environments such as open water tanks, reservoirs, lakes, oceans and skies.