Never heard of tidal rivers in EU. The map is not very accurate in some places. Another example is the area east of Notus - you'll appear to be in the lake on the map, but actually be on dry land.
The map rarely is accurate. You need to file a support case and beg them to update the map. As a matter of fact this should be part of the update process of FPC. If they change something on the continent, they should automatically update the map as well.
Back when I was running to get the TP at Athena Spacestation I thought that swimming there from the east around the southern beach was a good idea. Then I ended up swimming around some shore where the map showed the middle of the ocean around Eudoria...