Electronic navigation systems are now well established on commercial vessels throughout the world. In a big ship it is entirely feasible (and probably necessary) to design the system to suit the ship. Budgets are large and there are few space constraints, so that many separate displays may be used on a bridge which would not look out of place on the USS Enterprise. This is definitely not so for a small sailing cruiser or powered leisure craft. Neither is it true for many fishing vessels. It is to those with an interest in these small boats that I address this paper.