Final answer:
Viking ships helped their raids by being fast, agile, and able to navigate shallow waters.
Step-by-step explanation:
The Viking ships helped their raids to be so unexpected by utilizing their speed, agility, and ability to navigate shallow waters. The Vikings constructed various types of ships for different purposes, such as the longship for warfare and exploration, and larger merchant ships for trade. The longships had a narrow hull and shallow draft, allowing them to sail into shallow waters and surprise settlements along rivers and coasts.