Marpi Reef or Marpi Bank is a narrow seamount lies 28 km (17 mi) north of Saipan. With length of 9 km (5.6 mi) and 4 km (2.5 mi) in width, the reef is generally similar to the Tatsumi Reef south of Tinian in terms of orientation in a northeast to southwest. The peak of the seamount is at 26 fathoms or 53 m under water surfaces.