In 1872, he was on board the Phønix with the Danish Faeroer Expedition, and described the vertebrates and polychaetes of the Faroe Islands.
[2] The Phønix docked in Leith, and while in Edinburgh, Willemoes-Suhm met Charles Wyville Thomson, who would lead the Challenger expedition later that year.
[3] Willemoes-Suhm joined the Challenger expedition at the last minute,[4] and worked on many of the crustaceans that voyage discovered.
He died on 13 September 1875, during the journey from Hawaii to Tahiti,[5] and was buried at sea after a short illness with erysipelas.
[6] The genus Willemoesia is named after him, as is Suhm Island in Royal Sound (Kerguelen Archipelago), which was first charted on the voyage of the H.M.S.