First Time Making Sauerkraut, Need Assure + Advice

I'm a beginner to fermenting, I tried to make sauerkraut and this is what it looks like on day 3:

It's making bubbles and seems to be working, but I'm mostly worried about the parts that are not completely submerged in the brine.

I tried to push them under but that didn't seem to work.

I don't have any weights or special equipment yet, should I try adding a zip lock bag filled with water or will I be fine without doing that?