Some fleets grow one ship at a time, some grow by leaps in merger-­and-acquisition deals.

Lately, the top-five table of third-party ship managers has a new look, largely thanks to a wave of acquisitions of a particular type: the purchase of well-established shipowners' in-house technical units, with contracts attached.

India's Synergy Marine took its place among the top five in September with its acquisition of the technical management business of Maersk Tankers' 82 ships.