In the Boat Settings menu, you can set the minimum depth you’re happy to sail your boat in (your keel draught plus a safety clearance for example). Without this savvy navvy assumes a conservative safety depth of three metres.
Another thing to consider is that at the moment route calculations only take into consideration charted depths, without any tidal information. So it could be that at a particular time of day you know there’s enough depth clearance for your boat, but savvy navvy won’t let you drop a pin because it isn’t yet aware of the tides. Once we release the tidal calculation premium feature, it will know if and when you can start a route from that point.
You can change your boat settings by going into Boat Settings which can be accessed by clicking on the three horizontal line icon in the top left hand corner.