Comments about Pinnacle Pinnacle Endeavor Roller Bag:
I was looking for a diving gear bag that has both wheels/handle and backpack straps.
This bag is not too bulky, but it is big enough for a full set of scuba gear equipment (including large split fins) and some other relevant items (towel, books, underwater camera).
Putting together the backpack system needs some training - try that at home for the first time (and not at an unknown airport.
I also have the Kangaroo daypack which is very simple, but it zipped to the main bag, so carrying both is very easy.