This mod adds some simple building blocks that can be placed on top of liquid, making it easier to construct things on a body of water without needing to first build a piling from the ground underneath.
Wood pontoons are for building on the surface of water and steel pontoons can be placed on either water or lava.
There is also an option to add this property to wood and tree blocks to allow them to be used this way directly.
Works as advertised!
Note: This mod works well with MineClone2 / MineClone5 / Mineclonia.
It is not needed there though – the waterlily node has the same purpose.