[trux]

Yes, drunkinbda may be on the right track - almost all novices in freediving do the mistake that they bend their head, trying to look in the direction they swim, instead of keeping the head stright (in a relaxed position). Not only it leads to a worse blood supply of the brain, and can cause possible premature blackout, it adds a lot of drag, it adds to muscle tension and increases the oxygen consumption, but you also squeeze nerves in your spine which may be painful.