Near flowing lava players will float slightly upwards on blocks. This can also be used to clip into blocks above you for x-ray.

I have only noticed it with naturally flowing lava so far but u have to be one block below where the lava is flowing and you will start to float upwards slightly. if there is a block above you then it will stop you from floating but I found that if you can clip into a block above to the side of you x-ray is possible.