• waterproofed the cargo, 
• enabled the carrier to roll the cargo on and off the ship or deck.  

Problems with barrels:

• Where do you get a barrel and how much will that cost?
• Used commercial shipping boxes can usually be found for free;
• Not all cargo will fit in a barrel;
• A barrel holds less cargo by volume than boxes of the same width, length and height;
• If the barrel is more than 70 lbs the trucking company may require pickup by a truck with a lift-gate and an additional charge for providing a lift-gate;
• Boxes can be shipped by small parcel carriers without the "over-sized" charges that will be assessed on a barrel.

Conclusion:

• Boxes are usually a more cost effective method of shipping than barrels;
• If you are capable of transporting your barrel to/from the trucking or ocean cargo terminal, then the barrel rates are only slightly higher than shipping the same amount of cargo in boxes;
• Barrels are usually impractical for shipping by common parcel carriers and by international air cargo.
• An air cargo shipment may actually have a total transportation cost that is less than shipping your cargo in barrels.

Notes:

• 24 x 24 x 36 inches - standard 55 gallon shipping barrel;
• 12 cubic feet chargeable volume, 125 lbs chargeable weight;
• 9.4 cubic feet is the ACTUAL VOLUME of a 24 x 24 x 36 inch barrel