Nothing wrong with trading them, plenty of opportunity. The problem is that 90% of the time there are no shares to short so you're only participating on the long side.
The demand for coal shipments is growing exponentially. Coal is the second largest demand source for dry bulk shipping, representing 25% of all cargoes. At the end of last month, Dryships announced that it agreed to acquire a Newcastlemax drybulk carrier and a Suezmax tanker (both constructed in China).