Like the tankers, which sometimes they resemble, they are a specialised type of ship usually trading only between certain ports.
Njengemoto enkulu elayisha i- oyile nepetroli, ne-oyile ethi ngamanye amaxesha zifane, yayizincutshe zohlobo lwenqanawa ezidla ngokushishina ngaphakathi kwindawo yokumisa inqanawa.