An intragastric balloon and method of adding and/or removing fluid therefrom are disclosed. The intragastric balloon includes a shell, a grasping tab, and a self-sealing portion. A gastroscopic instrument which includes a grasping tool is inserted into the stomach of a patient and used to grasp the grasping tab located on the surface of the shell. Using the grasping tool, the intragastric balloon is securely fastened to the gastroscopic instrument. A filling instrument, such as a needle, is advanced through the self-sealing portion of the shell for the filling or deflating of the intragastric balloon. After inflation or deflation is complete, the filling instrument is then withdrawn from the balloon and the gastroscopic instrument withdrawn from the stomach.