Shallow water plugin, is an older plugin. Water plugin **is **being pushed to Preview 2, after they missed the Preview 1 deadline. I asked about the plugins on stream, and I was luckily answered that
Though Landmass plugin does appear to exist in Preview 1
Preview 1 is still a pretty early version of .26. Nearly everything is still WIP. Their aware of the bugs, and are actively working on them. No different from before the preview released.
We have many previews ahead of us.