Test at swimming school

The last week in every month is the examination day of swimming school called Itoman to move up to the next grade.  Kana failed grade 21 again which she has tried same test last month.  To pass it, her body must be kept straight floating on the water, but she can't.  Her legs goes down. The comment on her report card was written that she needs to relax her legs. So how can I tell her how to do it?  That's not easy, I think...  Floating is the first step for swimming as you know.  It would take time for her and I must wait until then.
I hope she will success the third test next month.