I am using iNavx for years. From the poor choices, it is the best boating navigation app, which I know. However, compared to my navigation apps in aviation, car driving, biking, hiking, running the quality is very poor: (1) the acquisition of maps is extremely bad; (2) there is no good way of switching between planning and navigating mode; (3) the menu structure as a whole does not make sense; there is a lot more... - I do hope that either iNavx or its competition solve the main issues soon