Do we forecast international trade by sea (marine transport)? No.
The Moody's Economy.com United States Forecast examines international trade as a whole, irrespective of shipping method. The Industry Forecast specifically examines air freight, railroads, and trucking, but not marine transport (seaborne trade) -- even though this accounts for a large fraction of world trade.
Why not? We are unable to obtain quality historical data (firm-level financials) on this topic. Most maritime shippers (APL, Evergreen, Maersk, etc.) are non-U.S. companies, operate under a variety of non-U.S. regulations, and report infrequently.
However, you may be interested in these alternatives: Our U.S. Employment, Output and Wages Forecast includes water transportation (deep sea, coastal and Great Lakes; inland) and support activities for it. Our Historical United States catalog includes container port traffic (TEUs) by port, and our Historical U.S. Detailed Trade database includes shipments by sea (value and quantity) by custom district.