I'm a ER nurse and I can tell you that Gillian would not have fractured a foot canonballing. The first thing to hit the water with a cannonball is your ass and then the force of the water pushes you back. Your feet wouldn't carry your weight and then collapse, crack or shatter. But jumping in from an upright position, feet first, and then landing on them, is what would most certainly crack it. Cannonballing sounds fun but it almost definitely isn't the way Gillian broke her foot.
Thanks nurse! And thank god she didn’t break her pretty rear.