It was a SKILLS DIVE..........I was not practicing under water basket weaving skills.
That could explain a lot. I really recommend working on those underwater basket weaving skills. If you do it mid water it will do wonders for your consumption rate on other skills. One skill that that I used to work on is stacking small rocks. It helped my diving immensely. I have no reason to doubt that underwater basket weaving would do the same for you.