This mod allows finer control over the spread of water and lava for the purpose of creating builds in creative with those fluids.
How do I use it?
Two game rules are added to Minecraft, doWaterSpread and doLavaSpread. By default these are set to true. Setting either of these to false will cause every block of that fluid to stop spreading. New fluids placed with this enabled will start flowing again once the gamerule is re-toggled and they are affected by a random tick.
The two client-side commands, /selectablefluids enable and /selectablefluids disable toggle a mode where fluids can be broken, and placed onto just like regular blocks. (Currently this only works on singleplayer worlds)