Catch This Embarrassing Moment on Camera

Image source: Barefoot Friends

A teenager accidentally falls off a 10-meter-high platform diving board. His friend whips out his camera and takes a picture when the teenager is halfway to the water below to commemorate the embarrassing event and posts it on Facebook. How many seconds after the teenager fell off did his friend take the picture?

Details and assumptions

• The acceleration of gravity is $-9.8~\mbox{m/s}^2$.
• Neglect the size of the teenager.