Marley Morrison’s knockout debut feature is a sharply observed coming-of-age story that will make you wince and laugh in painful recognition of universal truths       17-year-old AJ (Nell Barlow) is not one of life’s shiny, happy people       A family holiday at a caravan park in Dorset is her idea of hell       A moody misfit, she dresses for concealment and lets everyone know that she would rather be anywhere else       Then she spies flirty, free-spirited lifeguard Isla (Ella-Rae Smith) who might just be the girl of her dreams       Can AJ dare to take a first step on the road to happiness