[4][5] In 2003 he identified the mystery World War I U-boat off Trevose Head, Cornwall, as UB-65[6] by scraping the propellers to reveal the shipyard stamp.

[11] It shows the extent to which historical sources relating U-boat losses in UK waters in both world wars differ from the actual distribution of the known and identified wrecks.

This was published in Jutland 1916: The Archaeology of a Naval Battlefield,[12] for which he was awarded the 2016 Anderson Medal by the Society for Nautical Research.

[17] In May 2020 it was announced that the wreck of the landing craft LCT 326 had been found off Bardsey Island during surveys by Bangor University, in collaboration with McCartney.

[21] In September 2022 it was announced that the wreck of the liner SS Mesaba had been identified by McCartney in the Irish Sea during surveys by Bangor University.

The ship is famous for having radioed an ice warning, picked up by RMS Titanic which later struck an iceberg and sank with high loss of life in the North Atlantic Ocean.

SS Mesaba, LCT 326 and HMS Mercury are examples of the 273 shipwrecks surveyed by Bangor University and assessed by McCartney in a Leverhulme Trust-funded research project, published as a single-authored monograph, Echoes from the Deep.