The Paraguayans passed in a line parallel to the Brazilian fleet and continued downstream. Ordered by Meza, the entire fleet opened fire on the docked Brazilian steamers. The land troops, realizing that they were under attack, hastily boarded their own ships and began to return fire. One of the Paraguayan steamers was hit in the boiler, and one of the chatas (barges) was damaged as well. Once out of range, they turned upstream and anchored the barges, which formed a line in a very narrow part of the river. That was intended to trap the Brazilian fleet.
