- St. Pierre is approximately 704km from Mahé and 500km ENE from Aldabra (09 20′ S, 50 44′ E).
- St. Pierre is a small (approximately 1.2 x 2 km) raised coral island.
Guano was mined here between 1906 and 1972 converting a once densely forested island of Pisonia, to the current barren pitted landscape.
The western third of the island is now densely forested by Casuarina. St. Pierre is virtually inaccessible from the sea due to a steep undercut fossil coral shoreline that is only broken at one point. Here there is a small inlet (approx. 5m wide) to a sandy bottomed cove.
There is a derelict jetty and settlement on the north west shore that would only be accessible by boat in the calmest of weather.
Like all the other islands surveyed St. Pierre has a gently sloping seabed on the exposed south eastern coast and a steep drop off on the north west.