Compile Log Here
***leaked***
There is a leak in your map which prevents the rendering of the reflection for your water.
Just beneath your leak error is displayed the coordinates of the prop_dynamic that is "leaked".
If the prop_dynamic is located outside of the boundaries of your map, move it so that it's origin is within the boundaries.
Next, go to Map > Load Pointfile. Click yes on the pop up box that appears.
You should notice a distinct, red line in your 2D views.
Follow this line around to find gaps / openings / leaks in your map.
(By leak I mean an opening where light can go through / connects map to void)
Once you fix all of the leaks in your map, the water should work as you want.
Applying a cubemap is optional but may not look good if not used correctly.