i'm one hundred percent certain that after percy and annabeth made out underwater. and he wanted to make their relationship official. the question was not "will you be my girlfriend?" but "can i be your boyfriend?" i don't care what the canon says. percy gave annabeth the space to take the lead in the relationship. because after a lifetime of being abandoned by everyone she dared to care for. and then watching her on the brink of a panic attack at the thought of losing him the last four years. he wanted to honor a new beginning between them by follow her lead and moving at her pace.