De Dana Dan

Nitin Bankar (Akshay Kumar) and Ram Mishra (Sunil Shetty) are lucky in love, otherwise their life is a big zero as their bank balance. Nitin is stuck as a servant and driver of Kuljeet Kaur (Archana Puran Singh), according to the conditions of a loan which his father had taken to educate Nitin. Kuljeet is the owner of many malls, restaurants, and other places in Singapore, where this whole story is based. Nitin is fed up with Kuljeet's dog, Moolchand Ji, who always puts Nitin into trouble.
Ram works for a courier service in Singapore. He had originally gone there to work in Chinese films, but he was not selected. Anjali Kakkad (Katrina Kaif), is in love with Nitin and Manpreet Oberoi (Sameera Reddy) is in love with Ram. Both of their girlfriends are rich, and they put a condition â get money or forget us.
Inspector Wilson Parera (Sharat Saxena) is on the trail of Harbans Chadda (Paresh Rawal) who has nine arrest warrants due to cheque bounces. He is eager to get his son, Nonny Chadda (Chunkey Pandey) married, so that he can get dowry of the wedding and pay of all his debts. He finalises Nonny's wedding with Anjali, after her father, Kakkad (Tinu Anand), brings up the topic. Later at a casino, meets Mr. Oberoi (Manoj Joshi). After finding out that Oberoi is one of the richest Indians in Singapore, he lies to Oberoi to fix Nonny's wedding with Manpreet, which finally works out. As he didn't inform Kakkad, Kakkad gets really angry with Harbans. To counter Harbans, Kakkad fixes his daughter Anjali's wedding with someone else.
At the same casino where Harbans met Oberoi, Musa Heerapoorwala (Shakti Kapoor), decides to get married to Anu Chopra (Neha Dhupia), a dancer at that casino. After his brother-in-law finds out, he hires a Mafia Don, Maamu (Asrani), to kill Musa. Maamu sends his best assassin, Kaala Krishna Murali (Johnny Lever) to do the job. To hide from his wife, Musa books a room in Pan Pacific Hotel under the name Suber.
To get rid of all problems and earn some money, Nitin and Ram decide to kidnap Moolchand Ji, as that is the only thing 'living' that Kuljeet, the rich lady, loves. But things go wrong â after they reached Pan Pacific Hotel, the place where they decide to stay, they realise that Moolchand Ji has escaped, causing the police to believe that its Nitin who has been kidnapped. Things worsen when Anjali runs away from home and reaches their room. Initially, Kuljeet refuses to pay the ransom to the kidnappers, but after all her customers decide to go on a strike, she agrees to pay the ransom. As Nitin does not want to go back to Kuljeet, they come up with a plan â they decide to get a dead body from Maamu and throw it onto the railway tracks, along with his driving licence, and then spread the news that the kidnappers have killed Nitin.
Harbans' and Oberoi's families come to Pan Pacific Hotel, where the wedding is going to take place. Harbans and Oberoi click a photo to celebrate their families uniting. To give the advance money to Maamu, Nitin waits at the entrance of Pan Pacific, waiting for Maamu's man to come and say the code 'I'm Maamu's man'. But Kakkad arrives at the hotel, and chases Nitin into Harbans' room. Nitin tries to hide under the bed, but there is no place for him. At the same time, Harbans enters his room and to hide from Harbans, Nitin hides inside the wardrobe. Fed up of his calls, Harbans throws his mobile into the wardrobe and locks it, causing Nitin to get stuck in a wardrobe.
Paramjeet Singh Lamba's (Vikram Gokhale) room, who is the Indian Ambassador. Harbans mistakes Anu for Anjali, which causes great confusion later. Musa's photo, gets exchanged with Oberoi's photo, so Kaala tries to kill Oberoi. Wilson reaches Harbans' room and searches for Harbans, and opens the wardrobe to find Nitin, and mistakes him as Harbans. In an attempt to kill Oberoi, Kaala ends up falling onto Ram's and Nitin's truck, which they take to pick up the ransom. While picking up the ransom, Nitin gets left behind, and is taken to the hospital, while Ram takes the money and reaches the hotel, and Kaala is assumed to be the kidnapper, as he was on top of the truck. And to top it all, Maamu arrives at the hotel with a dead body that nobody wants. In the end, a bomb enters the water-tank of the hotel, which causes it to burst and make the hotel flood. At the end, Nitin, Anjali, Ram and Manpreet get the money and live happily ever after, even though nobody else is happy.

Question: What causes the hotel to flood?
Answer: A bomb in the water tank.