on my first (and only) eastbound trip from the Caribbean, on a 75-foot staysail ketch, the skipper put aboard diesel in 55-gallon drums . . . 4 at least, possibly 6 (don't recall, because he also fed us pink gins at noon). After Bermuda, he headed directly for the Azores High . . . millpond for day after day. We motored past the Azores . . . Approaching Gibraltar, we siphoned what was left into the tanks (which must have been huge anyway), then punched holes in the drums and tossed them overboard, because he didn't want to pay import duty on empty drums on arrival in Spain.
I can't imagine what would have happened if we'd run into heavy weather and one of the drums had broken loose. They were lashed down to beat the band, and the boat had waist-high bulwarks, not lifelines, but still . . .