The Mystery Sinking in the Midsummer Pool (1) Meitantei Conan : Season 1 Episode 787

Conan and his friends go to a hotel pool where Nagami, daughter of the president of Oiso Finance, drowns to death. She had been wearing a diving tank and searching the pool for her lost necklace. Based on the crime scene, Inspector Megure believes it may have been an accident. However, the hotel bellboys claim the body in the pool suddenly appeared.