Hmmmm....

OK, my completely unscientific answer -

First, I'll make the assumption that the suit fits in a way that the air can move around, otherwise it would be damned ucomfortable. We'll also assume no PFD.

Then, maybe it would be that it might matter if I jumped in feet first first or head first, based on the compression thingy. If feet first, I'm guessing the air would squirt to the top as I was entering the water. So, head is floating.

If head first (as you asked), maybe it would squirt to the legs. But I'm guessing the natural bouyancy in the rest of my body would ultimately bring my upper torso to the surface. I may not be able to put my legs down right away. The air might soon start to redistribute. But I wouldn't be stuck head completely down unless the rest of my body suddenly decided not to float at all.

And mind you I say this as somebody who looks like he has a lot of natural bouyancy but actually has the tendency to sink like a stone.

If one is wearing a pfd, then again, maybe you feet wouldn't sink but your head wouldn't either.

I'm starting to suspect that the reason for the question is merely to see if I'll jump off a pier...