Can someone help me find this movie?

I'm looking for a movie that should have about ten years but at least eight. The plot of the movie is a private investigator chasing two guys posing as important photographers in order to fuck young ladies.
I remember almost nothing of the film, except for the last scene. It was a foursome in a inner swimming pool.
There was two girls, one tall and blonde with big natural boobs and other girl shorter, with dark hair and small tits.
They were in bikini posing for the guys and then topless. The two girls entered in the pool to play a bit before they wereto the showers where the two guys try to convince them to have sex. They succeed because they take a gun each one and force them to suck their cocks. Sometimes between the sex scene appears the private investigator in his car driving to the pool to catch the guys.

One thing that I remember clearly it's that it was filmed in Marbella. In the beginning there is a road sign welcoming to Marbella (and I also believe that the word 'Marbella' formed part of title).

The last time I saw this scene was online. Maybe 4 or 5 years ago, one day that I remembered the movie and I wanted to rewatch it, so I searched and found it.

To finish, I think that it was a Private movie, but I'm not sure.