I wonder how differently Free! would have turned out if Rin had been the one to rescue Rei from the ocean? He goes for long runs, so what if he had been passing by as he did in the morning, obviously wanting to check on them, when he saw Rei? He was there at the joint practice, so he must have known Rei couldn’t swim, and with the obvious concern he shows for his friends would definitely carry over to their new member. And being a much stronger and nore practiced swimmer would most likely have enabled him to save Rei with no help from the others, rather they would just awake to find Rin having abandoned all pretenses of indifference towards them (most likely he would greet them both tearfully and joyfully after a traumatic experience) and Rei having found a new idol. The season would have the exact same sentiments, just six episodes sooner. (and happily skipping so much of the angst)