Between 1970 and 1997 when the Tui was in service for the navy she adopted Napier as her home port.
Originally the Tui was known as the USNS 'Charles H. Davis.' She was one of nine Conrad class oceanographic ships built for the United States Navy. She saw service with that navy between 1963 and 1970. She had been designed to perform acoustic experiments on sound transmission underwater, and for gravity, magnetism and deep-ocean floor studies.
In July 1970 she was offered and started her work in New Zealand. At first she was only on loan for 5 years. The loan was extended for another 5 years after which time she was leased for a further 15 years. She was recommissioned into our navy on the 11th of September 1970. Where she served as an oceanographic survey and research ship until her decommissioning in 1997. Tui was named after the New Zealand native bird the Tui. After being partly refitted and being installed with scientific equipment (which was then tested) she began working for the Defence Scientific Establishment in Auckland. For years Tui went about her work that she had been designed for, primarily underwater acoustics.
Tui worked in Australian, Indian Ocean and South Pacific waters. She had a busy work life working with Auckland University research, with DSIR scientists and other oceanographic ships. She also took part in several American research programs. Her acoustic research was mainly to do with the detection and tracking of submarines. She also made an extensive search for a reef which is now thought to be a phantom one.
In 1997, Tui was decommissioned. She was replaced by a hydrographic ship. Tui rests way up north and people are able to dive down to see her.