I see from LDS the Watkins name appears to be quite commonplace in NZ, many entries on immigration lists etc but nothing definite re this query. However I thought this may possibly be of future interest to Lorri, found while googling "Waitemata Harbour, Auckland, Watkins" (wrt the drowning). It takes a few secs to open http://www.ipenz.org.nz/heritage/conference/papers/Fitzmaurice_J.pdf

"This paper outlines the early unsanitary conditions in Auckland town in the 1850’s to 1870’s and describes the various proposals to alleviate the problems. Discharge was to the Waitemata Harbour at Okahu Bay. The scheme was commissioned in 1914. With increasing city expansion, the waters around the Orakei outfall became polluted and considered a menace to public health. In 1929 the Auckland and Suburban Drainage Board’s newly appointed Chief Engineer, H.H. Watkins,......." ??

There is a photo of H.H.Watkins suggesting him to be middle aged plus, and says he retired in 1947 (hopefully flushed with success).

Perhaps worth further investigation, clearly the Auckland Watkins were capable engineers !