Apparently some of the sails were quite sophisticated, not just pieces of cloth, but battened junk rigs with control lines running back to the handles of the wheelbarrow. This allowed the wheelbarrows to sail at an angle to the wind.
The Chinese wheelbarrow differed from the European wheelbarrow not only in the size of the wheel, bigger, but also in its placement. The load was balanced on the axle of the wheel which meant that on a level surface, the barrow driver only had to overcome friction. The total weight of the cargo was being carried by the wheel. On a European barrow, the kind that is still being sold here in stores, the weight is centered between the axle of the wheel and the handles, which forces the barrow driver to carry half the weight, limiting the use of the barrow to short trips.
In any case, check out this and other articles in low tech mag.
Which reminds me, every once in a while, you will see articles on wheelbarrow boats in the small boat magazines.
Unfortunately, the wheel is usually on one end of the boat and is small, which limits its use to short distances. With a larger wheel placed in a centerboard trunk, the boat could be transported a good distance. Of course we are now talking integral boat trailer, something which probably doesn't work as well as a conventional boat trailer and results in a boat which doesn't sail as well as a boat without an integral trailer. Perhaps I should just quit thinking about this concept. This sort of one thing does many things poorly design is something best left to the military procurement people.