Risk indicators provide an interesting way to compare chemical substances with respect to the risks of their largescaled release. The present study implies that, for antifouling agents used in commercial shipping, residence times in the marine biosphere are especially suitable to represent their inherent potential to cause exposure of organisms. A simple box model is described providing the possibility to estimate residence times in the marine biosphere from water-particle equilibrium partitioning constants and half-lives in water and sediment. Resulting residence times in the marine biosphere range from about 5 d (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one) up to about 40 000 yr (copper). For an evaluation of the validity of the model, calculated values are compared with measured environmental concentrations. Remaining uncertainties are also discussed. The main purpose of the presented residence times is to serve as a basis for decisions in antifouling paint development or environmentally conscious purchasing of antifouling paints.