The steps I provided above are common to any project since the multiplayer is a built-in inside the Engine. The only changes we do with blueprints is to set if they are replicated through network or not, and if so which variables should be replicated. The variables could be anything inside.
I have followed the steps above and the replication is fine for the waves and the reflections are ok too. The you are experiencing is really because the split screen is not a which allows the built-in multiplayer to work, since for it to work you need to network distinct process running in order to have an exchange of replicated values. So one single process can’t handle multiplayer from the core, but as two process which matches the real situation in real world it works perfectly!
Later I will post a small video showing the steps above in action, get back in 1 hour that the video should be up!
The link is bellow:
watch?v=-VqizBYxBGE