What does Exodus 7:19 mean?

The Lord said to Moses, 'Tell Aaron, “Take your staff and stretch out your hand over the waters of Egypt—over their rivers, canals, ponds, and all their pools—so they all turn to blood. There will be blood everywhere in Egypt, even in wooden buckets and stone jars.”' Exodus 7:19 - Modern Text Bible

(God tells Moses and Aaron to turn all the water in Egypt into blood, not just the Nile, showing the total impact of this sign.)