To set up the skript, you need

• Skript
• SkQuery
• skRayFall
• Multiverse(optionnal but recommended)

Create a FLAT world(With multiverse, or use default world)
/mv create CLASSIC NORMAL -t FLAT
In the world you want Throwback to be enabled
/registerThrowback

The plugin has a failsafe to prevent overflooding, it disable fluid phycics if 2500 blocks have been changed in the last 2 seconds.
You can manually Enable disable flow with
/stopflow
/resumeflow

Optionnally use 1.0 blocks by replacing originalblock with releaseblock in the skript