You can add locators to points on the ocean and use them as constraints or connect them to other attributes. For example, you can add individual locators and constrain them to the oars of a boat so they are affected by the motion of the water independently of the boat.
Dynamic locators follow the motion of the ocean in the Y direction, but additionally react appropriately to dynamic attributes (in the Extra Attributes section of the Attribute Editor).
The Create Dynamic Locator window appears.
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.