Transmission problem Lumina SS 2005 v8 5.7L

[Ghais_dery]

When turn on my car nothing happen. While I'm driving it after 5 minutes, the car turn on automatically to (N) but the gear box was on (D) and pressing the gaz but the wheels wont move what is the problem is't transmission problem or it's shaft problem

 

[CONROD]

Have the fluid level checked

 

[Ghais_dery]

Have the fluid level checked

Yes It was checked it was normal but the problem is that the fluid was mixid with water any idea about why it was mixid with water and how can I solve it