Not long after leaving HMS Conway, David went to sea as a cadet with the Blue Star Line (See the company's burgee, to the left), sailing to Russia, Argentina and Australia before "swallowing the anchor" in Cape Town.  However, he has never lost his love for the sea and ships, and among his radio documentaries have been Sails in the South, The South African Merchant Navy, and The National Sea Rescue Institute. A radio documentary, on his participation in the first Cape to Rio yacht race in 1971, Slow Boat to Brazil, is featured on the SANDEFJORD  page.

If he finally decided on a media career rather than a life at sea, his voyages to Russia, Argentina and Australia entailed valuable historical as well as maritime experience. Leningrad (now St Petersburg again) provided at least an introduction to life in the Soviet Union, while his visits to Rio Gallegos and Santa Cruz in Patagonia, aboard the same Patagonia Star which had taken him to Russia, showed him something of the unexpectedly freezing conditions in winter on the edge of the Pampas. Sailing on to Buenos Aires and La Plata, he witnessed the unrest which heralded a dramatic change in Argentina's history as Juan Peron prepared to flee Buenos Aires aboard a Paraguayan gunboat which would take him up the Paraná and Paraguay Rivers to asylum in the Paraguayan capital of Asunción.  However briefly, this visit also enabled David to practise his knowledge of Spanish, acquired in HMS Conway, as would a later visit to Argentine in 2009. Returning from Australia, his second ship, the Seattle Star entered the Suez Canal in a sandstorm in which only ghostly images of the nearest ships could be made out as wind-blown sand stuck to recently painted areas of the superstructure. Only months later, the canal would be blocked in a war between Egypt and Israel, which country was aided by British and French forces. Following the Arab-Israeli Six Day War of 1967, the canal would be closed again, this time for nearly eight years, through an Egyptian blockade.  This trapped 14 ships, including a Blue Star vessel, the Scottish Star.

As a radio journalist or crew member, or as a simple passenger, David sailed in the British liners Capetown Castle, Winchester Castle, and Windsor Castle; the Portuguese liner Infante Dom Henrique, and the Italian liner Africa, as well as in the South African submarine Johanna van der Merwe.