I don't understand: breathing deeply and using breathing for buoyancy control seem to contradict each other

[JoeTPhilly]

This video may be of interest:

 

[pdwh]

I am confused about how using breathing for buoyancy control interacts with breathing deeply to be efficient with air usage.

In my training dives I found that I was eventually able to stay in a relatively still horizontal position, without flapping my arms and legs around. However, when I took a deep breath in, I would go up, and when I breathed out again, I would go down. The only way for me to stop yoyo-ing up and down was to take small breaths in and out. The problem with that, of course is that it's a really inefficient use of air, due to dead space. The advice I see is to take deep breaths in and out (4, 5, 6 seconds each).

Could people help me see what I am missing here? How do I breath in and out deeply, without yoyo-ing up and down?

Thanks for asking the question. I've wondered the same thing and this thread has been pretty good and educational. I sing (took voice lessons, etc.) so that probably helped me quite a bit along the way but I've got a lot more to learn and practice. I guess I'll just have to dive more.