User Guide > Dynamics and Effects > Fluid Effects > Fluid Effects Menus > Fluid Effects > Fluid Effects > Pond >
Fluid Effects > Pond
> Add Dynamic Locator
Dynamic locators follow the motion of the pond in the Y direction, but additionally react appropriately to dynamic attributes (in the Extra Attributes section of the Attribute Editor).
Fluid Effects > Pond
> Add > Dynamic Locator > 
If you want to move the position of the locator interactively, the locator cannot be connected directly to the expression. In this case, turn on Free Transform.