The harbour of Port Curtis in Gladstone, Queensland, is being transformed by a massive dredging project. The initial target is to remove 46 million cubic metres of mud - enough to fill so many wheelbarrows they'd circle the earth. Gladstone has been an industrial port for several decades now, and there's evidence from other ports in the world that marine life can get sick if the heavy metals and mud are stirred up from the seafloor. However, the Gladstone Ports Corporation maintains that the turbid water from the dredging is within Australian water quality standards. Mark Horstman boards boats from opposite sides of the debate to see how water quality is monitored and whether all the dredging could be causing disease in fish and crabs.