Problem of negative volume
 

Hi!!!
I have to find the resistance of series 60 ship . I am using gambit for meshing the model. Every time when i mesh the model i get the "negative volume" with 2 or 3 inverted elements.So i can not use this mesh in fluent to get the result.Can any body tell me why i have the problem of "negative volume" and how can i fix this problem?
Sorry for my poor English :o

waiting for a response

thanks