@idefix37 thanks

@Tomber42
On given day/hour, wind wave and swell were collinear
so swell arrow overlaps wave arrow.
Now, at the same location, we have
8a16641d-1514-4170-b5ca-59ae9efb89cb-εικόνα.png

and on Thursday (noon) ....
8f988717-4e24-4e69-ae60-95f45c0c03d5-εικόνα.png

@idefix37 and @vsinceac, thank you both very much for the replies and information.

@saltyjoy
In Settings choose ‘Display directions as number’

24002704-E5F9-43AD-97E3-D2DFEA289E7A.jpeg

@bob71
The Swell2 arrow does not always show zero.
Here it shows 0.4m:

Capture d’écran 2020-07-22 à 10.22.30.png