First of all, his mass is irrelevant. Ignoring air resistance, all objects are subject to the same gravitational acceleration, regardless of mass.
Since this is clearly a homework problem, I'll try to get you going in the right direction, but it's up to you to work through the problem.
To figure out how fast the diver is traveling, you first need to find out how much time he spends in the air. You know the distance he falls; you know the acceleration of gravity. What's the formula that relates distance, acceleration, and time?
Once you know the time he spends falling, you just need to apply the formula that gives you velocity as a function of acceleration and time. What's that formula?
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