If you find they are bending in the middle and their bottom is sinking, encourage them to do 'banana tummies' where they push their bellies out. This generally has the desired effect of getting them flatter in the water.
World Rugby has reportedly conceded Aaron Smith's disallowed try in the World Cup final should have stood.
"It is not only useful for staff who are experienced but a valuable tool for those subject staff who have to take teams."
The variety of sessions across sports - sometimes we steal session ideas from one sport and use them with another.