The Persian Gulf, also known as the Arabian Gulf, is a mediterranean sea located in Western Asia. The body of water lies between Iran and the Arabian Peninsula and is an extension of the Indian Ocean. The Strait of Hormuz connects it to the Gulf of Oman in the east. The northwest shoreline is formed by the Shatt al-Arab river delta. The Persian Gulf features various fishing grounds, huge reefs (mainly stony, but also coral), and abundant pearl oysters, but industrialization and oil spills have harmed its environment. The current flooding of the basin began 15,000 years ago as a result of rising sea levels caused by Holocene glacial retreat.