About setup of Lake is described here.
(1) Enable LakeDisplaying of lakes is enabled when this check box is checked.
Uncheck this check box if you need a quick displaying since it takes much time for displaying lakes.(2) ComponentLibrary
specifies component of the lake.
Normally select one of the Water series.(3) Edit Component
When you want to change the material of the lake, or change the form of the waves, select this option.
The component editor will be invoked.
Please refer to Here for detail.