Any chance the profile you were using had the "snap to nearest road" option turned on? If that option was on for the profile then that would be why it jumped to the nearest road.
replyI've had the nautical navigation work fine when canoeing on rivers and streams where you're following linear features on the map. What it lacks is the ability to plot a sensible course across a polygon of open water.
replyRumor has it that routers have the same issue with highway areas so best practice is to add a "spine" to them
replyhttps://wiki.openstreetmap.org/wiki/Key:area:highway#Routers
https://wiki.openstreetmap.org/wiki/Proposal:Area_highway/ma...