Dear Ahmed,
As discussed in separate posts, the FSO component needs to properly set to avoid getting wrong (amplified) signal at the output of the component. The theory of the component is well described in the datasheet.
The LOS Channel component has limited range operation and has limited parameters to control. The model used in this component can be accessed in the datasheet as well. I am not sure if the component would work for short distances under water. You need to experimental verify that.
Regards,