Guy Lodge Film CriticFrom “Show Boat” through “Ship of Fools” to “Titanic,” if a certain strain of Hollywood melodrama has taught us anything, it’s that all of human life is to be found on a passenger boat — our dreams and desires and social differences somehow made clearer at some distance from dry land. Bangladeshi filmmaker Kamar Ahmad Simon applies much the same philosophy to his delightful documentary “Day After …,” albeit with the accompanying glamour removed.