A device (100) has surfaces (21, 22, 23, 24) and an anti-biofouling system (10) comprising at least one light source (11, 12) for performing an anti-biofouling action on at least a majority of the surfaces, the at least one light source (11, 12) being adapted to emit rays of anti-biofouling light. The surfaces (21, 22, 23, 24) are configured relative to each other and to the at least one light source (11, 12) such that during operation of the at least one light source, at least a majority of the surfaces (21, 22, 23, 24) is free from shadow with respect to the rays of anti-biofouling light from the at least one light source (11, 12), wherein it may be possible for the rays of anti-biofouling light to reach the surfaces (21, 22, 23, 24) by skimming along the surfaces (21, 22, 23, 24).