Hayden Brown , I was anticipating a reference to the danger of sharks lurking under water, off the coast of Australia.  You give good form to teachers as they consider PBLs.  Many teachers find that PBLs are shapeless, without form, yet you divide the term into useful categories that match specific learner needs and skills.  In my classroom, too, some students need strong support, while others can take an abstract idea and run well with it.  Your final two encouragements, to connect work to real-world cases and to local community experience, are wise; students soar when they see relevance, which is often a connection to the world they know (or think they know).  As an extra, I bring to your attention an outstanding book, contextualized in Australia, Rebecca Giggs' work Fathoms.  The World in the Whale.  This book brings the Little Big History project to a whole new level.  From observing a beached whale, she basically presents a total history narrative.  She is a remarkable writer.  I would be curious to learn what you think of the book.