SHANGHAI: The Xperia Z Ultra can be used underwater up to a depth of 1.5m, even allowing people to take pictures and film video in full HD below the surface, the company said.Launching it today, Sony claimed the handset, which has a 6.4-inch screen, has the biggest display and is the thinnest large-screen smartphone on the market.Calum MacDougall, Sony’s director of Xperia marketing, said: ‘The Xperia Z Ultra is the most exciting revolution in large-screen smartphone entertainment devices with both the slimmest and largest full HD smartphone display in the world that is second to none.’ The phone will include a Qualcomm Snapdragon 800 processor which Sony says is the world’s fastest processor.The screen also features handwriting recognition software that allows it to be used with pencil or stylus.The phone was launched today at the Mobile Asia Expo in Shanghai, alongside the Sony SmartWatch 2 SW2, a ‘second screen’ for any Android phone worn on the wrist. Sony say it will allow people to remotely handle calls, read emails, alter the volume on their music and even take pictures remotely using a built-in camera app.–MN