At the beginning you have to use trains, then you can take the boats, have them drop off the fuel at land, have the train pick it up, and bring it to the refineries. I made about 50000 a year per tanker by doing this in scotland. Also, since the competition uses alot of road vehicles, when i have enough money I buy armored trucks and make road blocks, it really works well.
Great game in almost every aspect~10 out of 10