For a brief period of time in infdev, water and lava were blocky. Later versions replaced the blockiness with the voxel type we know of today, meanwhile the blocky look was left behind.
Liquids looked like this:
https://cdn.discordapp.com/attachments/1386466173473783861/1386466173939482805/image.png?ex=68af803f&is=68ae2ebf&hm=72b196c656ce0a49dedb8986b31c22fa82f64e82949997c2d615c1fcba61586d&
I don't exactly care about how it is implemented, but personally I would prefer a simple render swap so liquids would become blocky like seen in those versions. What exactly I mean by this is that every water block would be replaced by its flat "puddle" state when rendered, keeping the water level.