In severely limited viz even with "only two" OW divers, if one has any issue you are probably going to loose sight of one of the two.
I have seen instructors leading a group on dive 3 (maybe dive 4) counting on a guide line marking the trail to keep students from getting lost in 10 ft viz They did not keep all students in visual contact. I was solo in the area of one such class diving solo and came across a student who had gotten lost and off the line. Took her back to rejoin her class at the anchor.
I have seen instructors leading a group on dive 3 (maybe dive 4) counting on a guide line marking the trail to keep students from getting lost in 10 ft viz They did not keep all students in visual contact. I was solo in the area of one such class diving solo and came across a student who had gotten lost and off the line. Took her back to rejoin her class at the anchor.