OILFIELD DEVELOPMENT AREA Numerous production platforms , underwater construction drilling rigs, diving tenders and support vessels exists within the other unlit objects and submerged obstructions , oil barges Oilfield Development Area enclosed by pecked lines. As all these features can not be charted, special caution should be oil derricks, only some of which carry lights and fog signals, exercised by vessels navigating in the vicinity . Vessels are advised not to enter these areas and those entering will do so at their own risk for which Government of India will not be liable in any way. The Government of India has established 500-metres Safety Zone around each installation in these areas. Mariners should not enter these Safety Zones . For details see Indian Notices to Mariners Special Edition No 21.