It's also something, for instance, the oval scutum seems to be adopted by the Romans really quite quickly after the Gallic invasion and the Battle of Allia in 390-387 BC.
If you're boarding an enemy ship, you're gonna have your scutum, and it's gonna be messy and nasty and slippery and difficult, but you're gonna fight as best you can, protecting yourself with your shield, striking with your sword.