James Charles Watermeyer was a son of Godfried Andreas Watermeyer, a brother of the surveyor Frederick Stephanus Watermeyer* junior, and a grandson of the well-known businessman Frederick Stephanus Watermeyer* senior. James Charles studied at the South African College, Cape Town, from 1878, passing the matriculation examination of the University of the Cape of Good Hope in 1881 and the intermediate examination for the Bachelor of Arts (BA) degree in 1883. Among others he studied chemistry under Professor P.D. Hahn*, but did not graduate. During the second half of 1884 he was appointed Professor Hahn's assistant in the College's Chemistry Department. He held this post until July 1889, when he was appointed government analyst and clerk under the Geological and Irrigation surveyor of the Cape Colony, Thomas C.J. Bain*. The post was created on Hahn's recommendation. Bain was very satisfied with the arrangement and included the result of Watermeyer's analyses as annexures to his annual reports for 1889 to 1892.
In October 1892 Watermeyer's post was transferred to the recently established Government Analytical Laboratory, headed by C.F. Juritz*, senior analyst of the Cape Colony. Three years later Watermeyer published some of his results in the Agricultural Journal of the Cape Colony (1895, Vol. 8(7), pp. 162-163) under the title "Systematic analysis of soils". In 1896 he took a year's unpaid leave and from October that year to September 1897 accompanied the German engineer Theodor Rehbock* on an expedition to study the water resources of German South West Africa (now Namibia) and their scientific exploitation. They spent eleven months in the central and southern parts of the territory. Upon his return to Cape Town Watermeyer presented a collection of rock specimens from Damaraland and Great Namaqualand to the South African Museum in Cape Town. He published a report on his work during the expedition, Deutsch-S?dwest-Afrika: seine wirtschaftlichen Verh?ltnisse... (German South West Africa: Its economic relationships; Berlin, 1898, 25p), as well as a good narrative account of the region visited and its agricultural potential, "Some notes on a journey in German South West Africa", in the Transactions of the South African Philosophical Society (1900, Vol. 11(1), pp. 19-33).
In March 1899 Watermeyer resigned from the Government Analytical Laboratory to take up an important position in the Imperial German Government in South West Africa. He was an early member of the South African Association for the Advancement of Science and an associate of the Chemical, Metallurgical and Mining Society of South Africa. He was killed in 1904, when war broke out between the Hereros and the Germans.