The Albedo $\alpha$ is the ratio of reflected to incoming radiation:

$$ \alpha = \frac { Q_{rs}} {Q_s} $$

The albedo of water for short wave incoming radiation is assumed to be 0.06 to 0.1, usually a value of 0.06 is assumed. This means that 6 $\%$ of incoming radiation are reflected. The rest is absorbed by water.