List of fields
|land||Standard ground, cannot walk through unwalkable cells on the ground. Can walk in shallow water, but not deep.|
|air||Flies in the air. Can travel over anything, including unwalkable cells (with the exception of other air units).|
|any_water||Unit may travel on any submerged cell, though not through unwalkable objects.|
|deep_water||Unit may only travel on deep submerged cells, and not through unwalkable objects. Deep is defined as the water deep enough for land units to not be able to pass through.|
|amphibious||Unit may travel on any land or submerged cell, but not through unwalkable objects.|
Because there is no way to require that a building be on both land and water yet, docks would have to have an "any_water" field. Land based units can still construct them provided they do so from shallow water or onshore, and this ensures that the docks are next to water, so they can produce their water units. Generally, ships produced from such a dock should be "any_water" too, as "deep_water" can be too restrictive to allow them to be produced. Currently, the AI has problems constructing docks this way, but has no problems with producing ships from docks like this, and Lua can place docks fine in scenarios.