A system for determining the location and/or orientation of a self-inflating or inflatable intragastric volume occupying device by ultrasound detection, the system comprising: an intragastric volume occupying device, comprising: a polymeric wall configured to have, under conditions of a gastric environment, a permeability to CO 2 of more than 10 cc/m 2 /day; and a valve system configured for introducing an initial fill fluid into a lumen of the intragastric volume occupying device in a gastric environment; and an ultrasound locating system comprising: an ultrasonic sensor configured to pulse sound waves and sense their return signal with a microphone located outside a user's body; and a computing system comprising a processor configured to receive return signals from the ultrasonic sensor sensed at various locations of the intragastric device after ingestion and a memory storing a pre-determined database comprising a plurality of known correlations between return signals sensed before ingestion of the intragastric volume occupying device and: locations on a user's body before the intragastric volume occupying device is swallowed, wherein the processor is configured to determine the location of the intragastric volume occupying device by comparing the return signals to the pre-determined database; and/or orientations of the intragastric volume occupying device, wherein the processor is configured to determine the orientation of the intragastric volume occupying device by comparing the return signals to the pre-determined database. an intragastric volume occupying device, comprising: a polymeric wall configured to have, under conditions of a gastric environment, a permeability to CO 2 of more than 10 cc/m 2 /day; and a valve system configured for introducing an initial fill fluid into a lumen of the intragastric volume occupying device in a gastric environment; and a polymeric wall configured to have, under conditions of a gastric environment, a permeability to CO 2 of more than 10 cc/m 2 /day; and a valve system configured for introducing an initial fill fluid into a lumen of the intragastric volume occupying device in a gastric environment; and an ultrasound locating system comprising: an ultrasonic sensor configured to pulse sound waves and sense their return signal with a microphone located outside a user's body; and a computing system comprising a processor configured to receive return signals from the ultrasonic sensor sensed at various locations of the intragastric device after ingestion and a memory storing a pre-determined database comprising a plurality of known correlations between return signals sensed before ingestion of the intragastric volume occupying device and: locations on a user's body before the intragastric volume occupying device is swallowed, wherein the processor is configured to determine the location of the intragastric volume occupying device by comparing the return signals to the pre-determined database; and/or orientations of the intragastric volume occupying device, wherein the processor is configured to determine the orientation of the intragastric volume occupying device by comparing the return signals to the pre-determined database. an ultrasonic sensor configured to pulse sound waves and sense their return signal with a microphone located outside a user's body; and a computing system comprising a processor configured to receive return signals from the ultrasonic sensor sensed at various locations of the intragastric device after ingestion and a memory storing a pre-determined database comprising a plurality of known correlations between return signals sensed before ingestion of the intragastric volume occupying device and: locations on a user's body before the intragastric volume occupying device is swallowed, wherein the processor is configured to determine the location of the intragastric volume occupying device by comparing the return signals to the pre-determined database; and/or orientations of the intragastric volume occupying device, wherein the processor is configured to determine the orientation of the intragastric volume occupying device by comparing the return signals to the pre-determined database. locations on a user's body before the intragastric volume occupying device is swallowed, wherein the processor is configured to determine the location of the intragastric volume occupying device by comparing the return signals to the pre-determined database; and/or orientations of the intragastric volume occupying device, wherein the processor is configured to determine the orientation of the intragastric volume occupying device by comparing the return signals to the pre-determined database.