"Boxes" fluid simulation

Someone knows why after bake a fluid simulation (resolution 280), unwanted boxes appears? I use an obstacle not low poly with volume setting as box that contain my fluid, and all fluid element set as free slip.

Nobody has this problem? Or am i a totally noob?

That’s just a limit of Blender, I guess. The resolution of the sim is simply not high enough. And you can’t with Blender.
I would suggest that you try using SPH particles and the Cubesurfer addon. It has some promising results.