The passage, "We . . . had great work to set [the barge] afloat, as our condition was such that much lighter things would have given us trouble" indicates that

Athe men were so weak that even something lighter than a barge would have been difficult to manage.

Bthe barge was much lighter than other things that might have given the men trouble.

Cthe men had a hard time getting the barge afloat because the Natives were giving them trouble.