Yesterday I was diving along my usual breakwall - trying mostly for closeups of the various denizens. All dives between say 3 and 10 meters with alot of adjusting for buoyancy by diving with less than full lungs. At some point there was a sense of release through the midsection - around the solar plexus - the feeling is like 'relief' - an almost giddy filling. Somewhere between intense relaxation and wanting to laugh. This accompanied very easy, long breathholds with normal discomfort toward the end.