Hull Cleaning

Hull cleaning is the removal of marine biological fouling — barnacles, mussels, seaweed, and slime — that accumulates on a vessel's underwater hull over time, together with the removal of degraded antifouling paint and any physical damage to the coating system. Fouling increases frictional resistance significantly, reducing speed and increasing fuel consumption and associated emissions; even a thin biofilm can increase fuel consumption by several percent. Hull cleaning is therefore both a commercial necessity and, under IMO's EEXI and CII regulations, an emissions management measure. Hull cleaning is carried out in drydock as part of a scheduled maintenance period, or in-water by divers using rotating brush systems. In-water cleaning practices are subject to increasing environmental regulation: many ports and jurisdictions restrict cleaning if it releases biocides or invasive species into the water. Biosecurity authorities in Australia and New Zealand have particularly strict requirements under their biofouling management rules. BIMCO's hull performance monitoring clause and OCIMF's TMSA framework both encourage shipowners to track hull and propeller performance using speed-power analysis to schedule cleaning optimally rather than at fixed calendar intervals.