HI,
actually I could do longer static in water, than on the surface. Paradow way, this can be help to get an explanation for your situation.
So, what I found is, that I could do longer static in the water, because I can relax better floating in the water. Of course this rather applies on the easy phase of the dive. (actually, I twice I fall asleep - early in the morning, while doing wet static, and woke up at 3 min, and continued a clear excersize
). So I think, that is why I can do longer wet static than dry.
Probably you do the dry static lying, and I suspect, you can relax better. Maybe you did more dry static, than wet (for me the opposite). So, when doing wet static you are more aware of doing something, you think more, so you are not relaxed enough. Maybe. If so, when more relaxed, you can better control your contractions, your contraction are not so strong, and consuees less O2.
I read, that you eliminated this factor, but think about it, on subconscios state you can be a a very litte (very-very little - if you do 6'30" !
) tense.
Also this tiny - non noticable little air move at the nose can explain some more seconds, as perow1 wrote.
