one extremely annoying thing is buddies which don't keep good buddy contact especially in low vis so they will go out of sight all the time and you have to look for them for a good moment just to find out that they were actually floating 4 meters DIRECTLY ABOVE YOU in 3 meter visibility
light communication can help this A LOT if
- they own a light in first place
- know how to communicate with it, at least a little bit
- understand why it is important to communicate with lights especially if not swimming on same level
.... but in those situations it would be much less stressful to just solo and not being worried about other person's health all the time and looking for them every couple of minutes
they didn't teach light communication or line deploying or dsmb shooting in OW course, I think they would be a must for every diver. And diving lights mandatory by law for every diver here
AND solo diving should be a mandatory part of normal diving courses just to make sure that ALL the divers can handle situations by themselves if necessary and not just rely on that their air carrying instabuddy will always be around WHEN they don't pay attention and run out of air