From the Introduction:
The basic design of the junk is truly ancient, and ships of this build are just as popular with pirates and smugglers as they are with traders and fishermen. Thus it is no wonder to see ships like this one dominating the local waters. Among the many advantages of these ship type are that it can be sailed with a small crew and that, without a keel, it has a low draft.
This particular ship in addition was built with a double hull and its interior is separated into several compartments. These two design features make the ship extraordinary hard to sink. The ships draft is extraordinary low even fully loaded allowing it to sail not only on the open sea but up rivers as well. Another feature gained by the low berth is that the ship can anchor in water too shallow for other ships of its size.
And although it could be sailed with as few as a handful of crewmen it can carry a considerably larger number of men. Considering all this, it comes as no big surprise that this junk is under the command of a less than reputable captain and carries contraband or pirates more often than merchants and trade goods.