You can separate bubble columns from the water block in bedrock edition using falling sand entities, basically, when you place a block and it's too close to an entity, the block can vanish a split second later. This can cause stuff like this to happen: (Refer to attached video)

To replicate this, get a small container with water and a soul sand underneeth as seen in the video, making sure there is a half slab allowing for you to interact with the soul sand after completing the next step.

After making the small bubble column, place 2 sand above it, letting them become falling sand entities.

Then place a block just above, leaving a one block gap to make the entities stabilize.

Finally, while this does not work 100% of the time (It's finicky, but it will work eventually), attempt to place any block on the soul sand. If done correctly, the block should disappear, leaving behind a separated bubble column.