The formula you need for this problem is

s(t) = s_{0} + v_{0}t - (1/2)gt^{2}

where s(t) is the height above ground 0 (the water) at time t, s_{0} is the initial height above ground 0, v_{0 }is the initial velocity and g is the acceleration due to gravity, 9.8m/sec/sec.

With that information you should be able to solve the problem...and yes, it wil give you a quadratic equaton.