Yeah, but you often have to update classes in a specific order, so you will just end up doing this:
if myEnemy.class=marine myEnemy.dostuff()
if myEnemy.class=troll myEnemy.dostuff()
if myEnemy.class=fish myEnemy.dostuff()
if myEnemy.class=marine myEnemy.dostuff()
if myEnemy.class=troll myEnemy.dostuff()
if myEnemy.class=fish myEnemy.dostuff()