teknitroxdiver
Contributor
Could be a CO2 buildup. Once upon a time I made a dive and for some reason (mainly lack of knowledge) I skip-breathed for most of it. Got back to the villa, crashed on the bed with a killer headache and some serious exhaustion. By the next morning I was fine. In the end I learned a whole lot about why you should NEVER skip breathe or do anything that causes a CO2 buildup, thankfully without any lasting effects.