A gastric bariatric balloon includes an upper balloon chamber for sealing against the fundus, a lower balloon chamber for sealing against the antrum and occupying the body of the stomach, and a supplementary chamber for filling at least a portion of the fundus. A tubular inlet is proximal the esophagus entry for receiving a hollow needle. This inlet is filled with a self-sealing material so that when punctured by the needle the material closes the needle hole upon withdrawal of the needle. Spaced apart voids in the material enable fluid interchange between the needle and each of the three chambers separately depending upon the depth of the needle within the inlet tube. Safety arms are mounted on the upper balloon chamber so as to prevent passage of the balloon through the pylorus in case of sudden deflation.