Île Platte, or Platte Island is 135 km south of Mahé

Mahé, Seychelles

Mahé is the largest island of the Seychelles, lying in the north east of the nation. The population of Mahé is 80,000. It contains the capital city of Victoria and accommodates 90% of the country's total population...

, the main island of the Seychelles

Seychelles

Seychelles , officially the Republic of Seychelles , is an island country spanning an archipelago of 115 islands in the Indian Ocean, some east of mainland Africa, northeast of the island of Madagascar....

. At 05°52′S 55°24′E, it is clearly south of the Seychelles Bank and belongs to the Outer Islands

Outer Islands (Seychelles)

The Outer Islands or Coralline Seychelles is a collective term for those islands of the Seychelles that are not on the shallow Seychelles Bank which defines the location of the Inner Islands. They are located at distances of 230 to 1150 km from the main Seychelles island of Mahé, and are all...

. Île Platte and Coëtivy Island

Coëtivy Island

Coëtivy Island is a small coral island in the Seychelles 290 km south of Mahe, at . Along with Île Platte, the nearest neighbor 171 km northwest, it comprises the Southern Coral Group and therefore belongs to the Outer Islands . Its area is 9.31 km² and it has a population of 252. It was named...

, 171 km further southeast, are together known by the collective term Southern Coral Group

Southern Coral Group

Southern Coral Group is a collective term for two islands of Outer Islands of the Seychelles, lying in the south of the island nation, between 135 and 300 kilometers south of the capital, Victoria, on Mahé Island.-Islands:...

.

The island, a low and wooded sand cay, is about 1250 meters long north-south, with a width from 250 m in the south to 550 m in the north, with a land area of 0.65 km². The island is bisected by a 900-meter-airfield that follow the long north-south axis. There is a small settlement on the western shore with the manager's house and a few guest cottages to the northwest.

Barrier reefs, over which the sea breaks heavily, extend 5 km north, about 0.8 km east, and 2.4 km south of the island, making it a pseudo-atoll

Atoll

An atoll is a coral island that encircles a lagoon partially or completely.- Usage :The word atoll comes from the Dhivehi word atholhu OED...

. Within the barrier reefs, the lagoon

Lagoon

A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...

is quite smooth, and landing is safe and easy. A submerged reef rim extends 12 km west and 18 km south of the island, obviously the remnants of a sunken atoll, creating a complex of almost 25 km in length north-south and 14 km in width east-west and covering an area of roughly 270 km².

There are two passages through the reef on the northwest side, available for small vessels with local knowledge only. La Perle Reef lies at the southwestern end of the reef rim, about 10 km southwest of Platte Island. Depths of less than four meters can exist on this reef where breakers have been observed.