During the brewing process, you may notice that your SCOBY ends up sinking. If this does happen to you, do not fret that it is just fine. The reason why it is okay is because a new SCOBY is going to grow across the top. But, the only potential issue is that if you have a weak SCOBY, it can take some time for a new one to grow across the top. The logical solution would be to prevent the SCOBY from ever sinking, in the first place.
The good news is if you bring both it and the tea to room temperature beforehand, it should not sink. You see, the difference in temperature is what causes it to sink and just a few degrees can cause it to.