Explanation: In the First Punic War, the Romans were total novices at naval engagements, and the Carthaginians ('Punics') were absolute masters of the sea. The Romans started the war without a fleet entirely! And only managed to build their first fleet by copying a Carthaginian shipwreck some hundred times, as they had no experts who knew what a seafaring design should exactly be! As one might expect, they were not masters of naval combat.
However, the Romans were quite skilled at combat at land. Marines at sea generally needed to be lightly armed, and well-trained (for the sake of keeping their sea legs when crossing from ship-to-ship). The solution? Slap a big board with railings and a giant nail in it on a crane on all of your ships - thus the corvus! Named as such because it vaguely resembled a raven's beak.
The corvus unbalanced the ships in bad weather and uneven seas, so it wasn't a long-term solution, but it worked long enough for the Romans to get their sea legs - 'til that time, the Romans inflicted a few stunning defeats by flooding enemy Carthaginian ships with heavily-armed Roman landlubbers!