Shields of the Athenian Marines?

[PMBardunias]

I am curious as to why many of you seem to think that here was a haphazard melee during shipboard combat. I find it more likely that men always fought in groups when possible, and the limitations on width imposed by the galley's beam make outflanking even a small wall of shields impossible. A mass of such shields would be of obvious value in repelling the boarding actions of the enemy. I think there are references to "shield-walls" on Viking ships in the Sagas, but someone will know better than I.