Marines: An "amphibious assault" is where a military unit can attack while getting off the boat, directly into another military unit or city. Only the US Marines think they can walk on water...
OCC: One City Challenge is a different style of play. It is "easier" in the sense that you only have one city to focus on, so there are far less units and improvements to work on. The challenge is in using limited resources to focus on research, trade and building. Since the AI civs will eclipse you in number of citizens you will be near the bottom of the pack, but that permits alliances and tech-trading. If you exploit the KeyCiv concept you will only be facing the minimum range of beakers for each tech, but there is no extra bonus for having only one city. One unique aspect of OCC is that your city is impervious to Barb attack as look as you have at least one unit of any type inside (even a caravan or Dip will do).
