Personalities--alpha, beta, or gamma?

Bruce Willis, Tears of the Sun
As we all know, a SEAL team took out Osama bin Laden. I believe it was also a SEAL team that shot the Somali pirates, the ones who took the ship captain prisoner. SEALs seem to be the supermen of our day—no wonder they're featured in so many romantic suspense novels. I wonder what sort of personalities they have in real life. In books they're always alpha males