For comparison I suspect you could easily get 1$ a gallon by just selling that gas. Using a mid sized fishing boat you could probably move ~1 to 10k gallons from the ships's fuel tank to a near by country without that seeming odd. Make that trip once a week and your living the good life without doing anything 'odd.' Hell I suspect you could simply meeting other fishing boats at sea fill their tanks for cash or even fish which would be next to impossible to catch.