Location and features
The Semporna Islands are situated at the entrance to Darvel Bay, off the east coast of Sabah, Malaysia. The main islands of Bodgaya (796ha) and Boheydulang (313ha) are remnants of an extinct volcano. The crater is now flooded with seawater to form a large lagoon 25m deep. The southern side of the lagoon is open but just below the surface is a long stretch of reef which represents the southern crater rim.
Bodgaya and Boheydulang © Videographics Productions
To the west of the central islands is an extensive reef with two smaller islands in the form of raised limestone platforms (Sebangkat (51ha) and Selakan (32ha)). This complex is separated from the ‘Bodgaya volcano’ by a 50m deep channel, but is probably part of the same formation, for example the remnants of a subsidiary (lower) volcano. Evidence for this comes from the atoll-like shape of the reef and also the presence of a hill of volcanic rock at the northern end of Selakan.
Sebangkat © Videographics Productions
Maiga, Sibuan and Mantabuan are sand cays built from the eroded remains of the surrounding coral reefs. Each has an elevation above sea level of about 1-2m and is situated at the southern end of their respective reef which is generally oval to elongate in shape. Also within the area is a bank reef (Mantabuan) and two patch reefs (Church Reef and Kapikan Reef), which may be submerged reefs originally associated with mounds on the seabed.
Mantabuan Island © Elizabeth Wood