Also note that on two seperate occasions attempts to colonise Gardener Island were thwarted by the problem of insufficient freshwater supply...
"In 1856 Nikumaroro was claimed as "Kemins Island" by CA Williams & Co. of New London, Connecticut under the American Guano Islands Act. There is no record of guano deposits ever being exploited, however.[2] On 28 May 1892, the island was claimed by the United Kingdom during a call by HMS Curacoa. Almost immediately a license was granted to Pacific entrepreneur John T. Arundel for planting coconuts. Twenty-nine islanders were settled there and some structures with corrugated iron roofs constructed, but a severe drought resulted in the prompt failure of this project within a year. In 1916 it was leased to a Captain Allen, but remained uninhabited until 1938."
And
"On 1 December 1938, members of the British Pacific Islands Survey Expedition arrived to evaluate the island as a possible location for either seaplane landings or an airfield. On 20 December, more British officials arrived with 20 Gilbertese settlers in the last colonial expansion of the British Empire.[N 2] Efforts to clear land and plant coconuts were hindered by a profound lack of drinking water. By June 1939, a few wells had been successfully established and there were 58 I-Kiribati on Gardner, including 16 women and 26 children. The island's early supervisor and magistrate was Teng Koata whose wife, according to local legend, had an encounter with the goddess Manganibuka on a remote part of the island.[citation needed]
The British colonial officer, Gerald Gallagher, established a headquarters of the Phoenix Islands Settlement Scheme in the village located on the island's western end, on the south side of the largest entrance to the lagoon.[N 3] Wide coral-gravel streets and a parade ground were laid out and important structures included a thatched administration house, wood-frame cooperative store and a radio shack. Gallagher died and was buried on the island in 1941.[7] From 1944 through 1945 the United States Coast Guard operated a navigational LORAN station with 25 crewmen on the southeastern tip of Gardner, installing an antenna system, quonset huts and some smaller structures.[8] Only scattered debris remains on the site.
The island's population reached a high of approximately 100 by the mid-1950s. However, by the early 1960s, periodic drought and an unstable freshwater lens had thwarted the struggling colony. Its residents were evacuated to the Solomon Islands by the British in 1963 and by 1965 Gardner was officially uninhabited."
So, freshwater was always a problem, even with all the right equipment and regular visits from supply ships. Now, put two non-survival trained persons there and what are the chances of them succeeding where all others mentioned previously have failed? It's just a thought