Crime fiction
Mahendra described the film as a suspense thriller, while N. Venkateswaran of "The Times of India" described it as a psychological thriller. Devika Bai, writing for the "New Straits Times", referred to it as a whodunit film. In the 2017 book "Indian Horror Cinema", Mithuraaj Dhusiya likened it to a slasher film because of the numerous prostitutes murdered by Chandru. K. Hariharan, director of the L. V. Prasad Film &amp; TV Academy, noted that sexuality and the repression of desire were the dominant motifs in "Moodu Pani", expressed through the mysterious misty atmospheres of Ooty where the protagonist confronts their psychological antagonist. He also noted that "Moodu Pani", like many of Mahendra's films, borrowed its themes and stylistic devices from French New Wave and New Hollywood styles of filmmaking. Ilangovan noted that Chandru's character, which was depicted as having flashes of wickedness bordering on perversion, was new to Tamil cinema. Crime fiction writer Pattukkottai Prabakar considers "Moodu Pani", along with "Sigappu Rojakkal" and "Nooravathu Naal" (1984), to explore the personalities and behavioural traits of psychopaths in detail.