Thalassamania:I agree, it's a question of how far does someone have to swim for an instructor to be able to evaluate. But ... in the first 50 yards I can tell you who's "teachable" but it often takes further and a little tiredness to tell you who's "not yet teachable."
Evaluate what? If it's not confidence and it's not stamina, what is the point of the swim?
kari