Answer
$L=v_{0}\times t=2\frac{m}{s}\times0.8s=1.6m$
Work Step by Step
Assuming there is no air friction, the horizontal velocity of diver will not change because there is no horizontal force acting on him.
So the horizontal velocity of diver will be the initial velocity. So after $t=0.8s$. he will travel $L=v_{0}\times t=2\frac{m}{s}\times0.8s=1.6m$
