McCarthy and Vincent were able seamen whose specific selection has been explained in various ways in the historical accounts. Vincent was the strongest man on the expedition, physically; McCarthy was among the steadiest. Neither explanation is entirely satisfying — there were other strong men and other steady ones — and the full reasoning behind the crew selection is not recoverable from the surviving accounts. What is recoverable is that the six-man crew sailed, and that they made it.
The 22 men who stayed on the island helped load the James Caird. They manhandled the heavy boat down to the water’s edge, loaded the stores, steadied it against the waves. The departure was not quick or clean; it was the kind of effortful, cooperative, multiple-attempt departure that small-boat launches in surf are always likely to be. The boat was loaded and launched and loaded again after a wave swamped it on the first attempt. Eventually the six men were in the boat and pulling away from the island, and the 22 men on the shore were watching them go.
There is no account of what was said at the moment of departure that can be verified as exactly what was said. The accounts written afterward report that Shackleton told Wild what to do if rescue didn’t come — that Wild was authorized to decide when to launch one of the remaining boats. Wild’s own account says that Shackleton left him in command and told him to do his best. The exact words are less important than the fact: they were dividing. Six were going to try for the impossible and 22 were staying to wait.