Our system has worked well for many years, and consists of a hard pelican carry on for my camera and related gear, two backpacks and a smaller roller carry on which we use as a cabin bag. The camera bag and the two backpacks go into the overhead bins without difficulty, and the small bag stays at our feet. We put all necessary items in the backpacks, such as mask, regulators, a change of clothes, etc. Our bulky gear (BC's, suits, fins, most of our clothes and such) goes into checked bags. I have had to gate check the pelican bag a few times, especially when using asian based airlines. Usually, however, it all goes through with no problems.