Ko Muk or ˉPearl Islandˇ lies 13km (8 miles) due south of Trangˇs Pak Meng Pier. Until fairly recently a remote back-packer destination with a small resident population of Chao Lae ˉSea Gypsiesˇ, Ko Muk is fast developing into a more up-market destination. Tham Morakot or ˉEmerald Caveˇ is a major local attraction. Visitors have to swim about 75 meters (240 ft) through a water-filled cavern at high tide, part of the swim being in virtual pitch darkness, to reach a hong or sea-filled lagoon that is otherwise shut off from the outside world, with the only access other than the tunnel being by the inaccessible heights of the collapsed dome allowing sunlight into the lagoon below. Boats can also enter the lagoon, which has a small white sand beach, at low tide. The east coast of the island is undeveloped by tourism and remains the domain of the local fisherfolk including Chao Lae. Trang province was dependent on tin mining until the first rubber seedlings were brought into Thailand around 1901  part of a long journey from South America via the neighboring Malay States. Rubber, palm oil and fishing are the mainstays of the province's economy. Tourism is making an increasing impact as Trangˇs Anadaman Coast and islands are increasingly developed and popularized.