Tallships, massive deep ocean going vessels made for deep ocean travel and war.
The Gallic Veneti of Armorica were great traders, raiders, and pirates. This was largely due to the great quality of their Pontones; truly massive ships of the age. Crewed by the skilled warrior Veneti, they are more than capable of dealing with numerous threats at sea. Their thick hulls could repel any weapon of the period short of burning pitch, and their huge size makes it nearly impossible to strike at the crew. They are most reminiscent of later period 'galleons' in their size and purpose, and they would confer a definite edge to any commander who employed them. The Veneti were eventually defeated by Caesar in a climatic sea battle, where Caesar, recognizing that his own ships stood little chance against the great ships, developed different tactics to overcome them.