Both builders specialised in the construction of dredgers and hopper barges. The buckets-ladders are used in bucket elevators or in the dredge design of some dredgers. SCA operates some 60 ships and boats, such as tugs, dredgers, cranes, and smaller boats. Barkmeijer mostly builds dry cargo vessels, dredgers, and tankers and specialises in custom builds. He also built a barge powered by paddle wheels and several dredgers. Robbs was notable for building small-to-medium sized vessels, particularly tugs and dredgers. Small backhoe dredgers can be track-mounted and work from the bank of ditches. The estuary is regularly dredged by Padstow Harbour Commission's dredgers, "Sandsnipe" and "Mannin". Where long-term erosion is identified, beach nourishment using high-capacity suction dredgers is deployed. Ships, dredgers, other floating craft and even a bridge were sunk to block the canal. The dredgers remove sand from ship channels and pump it toward the fort. Between 2002 and 2007, ten major dredgers were added to the DEME fleet. They were the first dredgers in the Netherlands to maintain the harbour at Velsen. The environmental damage caused by the dredgers is enormous. Cameron personally led an expedition against the illegal dredgers.