Here is a tutorial to make the water move up and down in your map, like in my mod OceanTide Steam Workshop::☠ OceanTide - TheIsland ☠
The tuto is almost finished, I just have to add more details if needed.
Please have a look at the source here : [WIP] Ocean Tide - ARK: Survival Evolved - Unreal Engine Forums
- Locate your PhysicsVolumes and get their Z location :
To do that, edit->copy a PhysicsVolume that is a part of the Ocean…
… and paste in a text editor.
Please note the Z value in the line RelativeLocation, it will be base offset for this Volumes.
/!\ Make sure all your PhysicsVolumes are MOVABLE in the detail panel, NOT STATIC, or they will never move. /!\
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Do the same for WaterPlane
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Do the same for PostProcessing Volume
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Modify main blueprint code :
Here is the EventGraph : When the game begins, identify all Volumes and waterplane that compose your ocean, to store their reference, then set a timer that repetitively execute the function “Move_ocean”.
and the detail of its related functions

You will also need to add 4 variables : an array of strings to store the names of your PhysicsVolumes, waterPlaneActor, water_postprocessing_actor, and an array to store all your volumes reference for fast access.
Please have a look at the source here : [WIP] Ocean Tide - ARK: Survival Evolved - Unreal Engine Forums