Nikumaroro is a typical coral atoll island with a lagoon surrounded by a ribbon of coral. The lagoon at Niku is approximately 3 miles long and a mile wide at its widest point. There are two channels that connect the lagoon with the ocean both on the southwestern side of the island, Tatiman Passage (pronounced Taziman) to the north, and Baureke Passage to the south. Baureke passage is on occasion blocked and dry as we found during the Niku IIII expedition in 2001 (and seen in the satellite photo below), but was flowing in 2007 when NIku V visited the island.
The lagoon is generally fairly shallow with an average depth of 15 ft, and a maximum depth of no more than 20 feet. There are coral heads to be found sporadically, and the bottom is generally a deep layer of very fine silt that can be stirred up during periods of windy weather reducing visibility underwater to virtually nil and giving the lagoon a milky quality. The temperature of the water is in the 90° F range. Beyond coral, there are a wide variety of marine animals that live in the lagoon including fish, turtles, crabs, Tridacna and other clams, and sharks (generally juvenile black tip reef sharks up to about 3 ft in length).
The lagoon can best be understood by looking at the 2001 satellite photo of Nikumaroro.
The Satellite Photo
Leading up to the 2001 expedition, TIGHAR was able to obtain a high resolution satellite photo of Nikumaroro that proved to be an excellent research tool.
GPS Data and the Start of the NIku GIS Project
NIKU IIII was the the first year during which multiple Expedition Team Members brought with them handheld personal GPS units. Many waypoints were logged during the trip and collated after the expedition. The data has been overlaid by James Thompson of Select GIS Services onto a copy of the second 2001 Sat photo (post expedition) as you will see below.
During Niku IIII in 2001, TIGHAR dive team members Van Hunn, Walt Holm, and Andrew McKenna surveyed the NW end of the lagoon from the passage inlet delta of sand to the NW corner by using a 16 ft aluminum boat with outboard motor to pull two divers on manta boards. The two divers would skim the bottom of the lagoon searching for any unusual objects to be found. The survey utilized a series of markers and GPS waypoints to systematically cover the entire NW end of the Lagoon. See the tan dots in the overlay of the sat photo below.