Complex sentence: For the first two days out of the village, the Spaniards were not attacked, but once they were up to their chests in water in the swamp, the Apalachee attacked them with a shower of arrows.
Split into simpler sentences: For the first two days out of the village, the Spaniards were not attacked. When they were up to their chests in water in the swamp, the Apalachee attacked them with a shower of arrows.