Starting in 18w07b, it was possible to add waterlog attributes to any blocks through a data pack. However, this no longer works beginning at 18w10d.
Here is a reddit post about it: https://www.reddit.com/r/Minecraft/comments/7xrxne/swimming_through_the_sky_in_18w07b_using_the/
MC-128004
making blocks waterlogged through data packs no longer works
Resolved
Works As Intended
0
Yes. This will be a great addition. Or fixing this bug. Or adding "Waterlogged" State to all blocks, but only blocks defined in data packs can use this state to be Waterlogged. Anyways, I'll download the snapshot from the Wiki. Older, but with good feature.