The crew had to sail the ship to Africa, help with the buying of enslaved Africans, guard and care for those already bought, sail the ship to the Americas, help with unloading and loading, then sail the ship home. A slave ship took a large crew out to Africa: the numbers were needed to look after the enslaved Africans. Once the ship reached the Americas, and the enslaved Africans were unloaded, there was no need of a large crew to sail the ship back with a cargo of sugar in barrels - so the captain often laid off some of the crew to save money on the return voyage.

In this detail from 'A View of ye Jason privateer', the crew are loading a boat with newly-purchased men. The ships usually anchored off-shore and all business was done either by the captain going ashore or by the local merchants coming out to the ship in their canoes. It was hard work for the sailors unused to the tropical climate. The slave trader Isaac Hobhouse told his captain to pay a small fee for the merchants to bring enslaved Africans out to the ship 'which charge had rather be at than fatigue the men to row so many leagues, which frequently has hurried em into sickness and fevers.'