Do you know a simple fast front-end MD software for OS X I need a GUI front-end simple MD software for OS X, something similar to ascalaph maybe.

What I need to do is a rigid optimization of waters around a protein. I don't have many water molecules around, so a few tips about how to not let them fly away would be nice too.
I'm biased, but I recommend Avogadro which can do simple force field optimization using MMFF94 or GAFF. It's not MD, but it would certainly work. It runs on Mac.

The water molecules shouldn't "fly away" during minimization, since there should be hydrogen-bond and Van der Waals terms attracting them to each other and to the protein.

I'll also point out that VMD runs on Mac and are quite easy to use. It can set up MD calculations with NAMD, GROMACS, etc.