Continuous relative localization among all local members of a school of submarines is an essential pre-condition for distributed motion control. Exploiting the short-range, underwater electromagnetic as well as the acoustical channel, the proposed approach delivers sufficient bearing, range and posture estimations based on local sensing in small, autonomous submersibles with limited energy capacities and computational resources. This research is part of the Serafina project at the Australian National University, aiming for large schools of autonomous underwater vehicles.