The visibility of the aliens during the port map is a little off. There are several ships with railings which seem to provide the aliens with complete visual cover. I can't see them unless the character is on the deck of the ship. The worst case of this was on the barge. The deck of the barge is clearly below the dock level but the alien popped into view, shot, and disappeared again. When the character went down onto the ship, the alien was only 2 squares away from the entrance - should have been visible.
Man what a fun game.