Unexploded goats?
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
I've pretty much had it with this thread, but I complement you on that insight.
Not only overall physical efficiency (COPD as an extreme case) but simple position and breathing style matter too. Please watch the two layman vids offered below while keeping in mind two very different trims and procedures, diving vertically and breathing shallowly vs. diving horizontally with diaphragmatic breathing: