@anonymous_user_80fdc16f That would be a really long post, try googling tutorials for performance debugging.
For starters these are the most useful console commands, give them a try one by one:
stat game
stat rhi
stat GPU
stat SceneRendering
Maybe you’ll see something out of the ordinary. The memory can be seen in your task manager (windows) / activity monitor (mac). Or you can try the Visual Studio tools but that took me a long time to figure out and now I’m not even sure I would be able to replicate it again myself. 
I’ve removed the plugin and decided to try the new official water feature of 4.26.