In July, Marmaduke met with two shallops of the Mary Margaret, a ship sent by the Muscovy Company to hunt whales, in Horn Sound.
Later, the Elizabeth, Jonas Poole, master and pilot, sailed into the bay and attempted to shift his cargo to enable him to accommodate the goods of the Mary Margaret, but in doing so his ship capsized, forcing the crew of both the Mary Margaret and the Elizabeth to sail home in the Hopewell.
All we know is that he carried off the post and arms set up on Spitsbergen's northwest coast by Barentsz in 1596, and that he reached Red Beach (the shore of Breibogen) and as far as Gråhuken (Grey Hook) at the western entrance of Wijdefjorden, where, in early August 1614, Robert Fotherby and William Baffin found a cross engraved with the name Laurence Prestwood, as well as two or three others, dated 17 August 1612.
On speaking with the English admiral, Benjamin Joseph, on his intentions of sailing around Point Lookout (Sørkapp) for further exploration, he was told "that he had hindered the voyage more by his absence than his discoveries would profit" and was ordered to return to the Foreland.
He sailed once more for the Company as master of the Heartsease the next season (1614), exploring northeastwards over the northwest coast of Spitsbergen at least as far as Gråhuken, where Fotherby and Baffin encountered some of his crew in a shallop.
In 1617 Marmaduke petitioned to King James that he could prove that the shortest route to Cathay (China) was to the north-east.
In the 2007 novel The Solitude of Thomas Cave, by Georgina Harding, Marmaduke appears as captain of the Heartsease, which is sent to Edgeøya in 1616.