Filmmaker Anubhav Sinha gave the media a sneak peek of his debut production venture "Warning" by unveiling its trailer here Wednesday. He admitted he was very scared.

The movie has been produced under Sinha's banner Benaras Mediaworks.

He was hesitant about showing the trailer, and said that he was feeling just as scared as how he felt when his first directorial "Tum Bin" was being presented to the audience in 2001.

"I have wanted to produce films for a while as I cannot make all the films I want to make as a director. I am so scared while releasing the trailer today...I felt like this during 'Tum Bin' as well," he said during the trailer launch of the film here Wednesday.

Production was a tough experience for Sinha, who said that it required a huge amount of belief in the project.

"This was tough. It requires an immense amount of belief in the subject matter and the people. I want to thank all my producers in the past. I realise how tough it was," he said.

Sinha also added that this was the toughest film he has made.

"It is a small, but a tough film. I hope to make another one next year," he said.

Based on a true story, a huge portion of the film has been shot underwater, and he admits it was indeed difficult for the team.

"The actors had to stay in the water (almost) all the time. It was not easy for them as well," he said.

"Warning" is a 3D horror film and stars Santosh Barmola, Suzana Rodrigues, Varun Sharma, Manjari Phadnis, Jitin Gulati, Sumit Suri and Madhurima Tuli. It will release Sep 27.