Gwilliam on Family Tree Circles

So far have not been able to find where or when my grandfather Alfred Pimm came to New Zealand. His gravestone says he was an AB in the merchant Navy in the 1914-18 War. At a loss as to where to go. He worked as a fireman on Shaw Saville vessels trading between Australia and NZ. He was born to Henry and Elizabeth Pimm in 1901 at West Ham, Essex, England and married in NZ to Elsie Chalmers McLaren in Dunedin, NZ, and later to Rita Eleanor. Appreciate any help on this.