Maybe the reason they came by sea is a giant crack splits the main highway into town in two, leaving a ditch with depths of up to 30 feet.

Also, the Marine helicopters began landing just before noon on Tuesday.

The following tells why things are moving at the pace they are.

International aid workers and supplies have poured into Haiti in the last few days, but the country’s ruptured communications, poor roads, and chaos in the rubble-strewn capital have made it difficult to get help and information to the people, especially out in rural areas.