You can place a water source inside of leaves. This might work as intended because the leaves change to a bit blue. It will leak through but the main source of water is inside the leaves and can still be picked up.

Steps to reproduce:

1. Place leaves
2. Place water inside the leaves
3. Although the water leaks, it should be inside the leaves

Observed results: the water is inside the leaves and can be picked up too

Expected results: the water will be placed on top if the leaves not inside

Side notes: if leaves are waterlogged  this might be the issue however I can place the main water source in the leaves