After he became satisfied that they had memorized the prayer, the Bishop left the island instructing the hermits to pray as he had taught them and returned by the rowboat to the fisherman's vessel anchored offshore to continue the voyage.
The Bishop left the island. This island was instructing the hermits. This was to pray as he had taught them and returned by the rowboat to the fisherman's vessel anchored offshore to continue the voyage. They had memorized the prayer. He became satisfied this.