doubt on editmask

[uranoscopus]

Hi everybody, I have a doubt on the editmask tool.

I generated my grid by using seagrid but initially setting all the points as seapoints.
Then I generated a land mask for rho_points just using bathymetry as filter (not in seagrid).
After that, to refine the mask, I used the editmask tool, that works fine at first look.
But, after the refining was done (I think it works on the mask_rho) the tool saves also mask_u mask_v and mask_psi. Mask_u and Mask_v appear really weird, like they were inclined of 45° right and left.

Anyone knows anything about that?
Cheers,
Antonio