am I being mean?

was swimming with my friend today. One of her goals is to dive and touch the bottom of the deep end of the pool, around 9 ft. Shes a smoker so she cant control her breathing very well. Everytime she tries to swim down, she floats back up. She never makes it past 3 ft below surface. She's been very confused how to control her breathing so she can sink down properly and touch the bottom.

I havent the courage to tell her scientifically fat is less dense than water so someone with a significant amount of it will float on water and it isnt her breathing that is the problem......