I've done most dives in warm water and never had problem clearing my ears. On two occasions I had trouble and had to either abort the dive or stay around 15 feet where my ears were not bothering me. I realized that both times the water temperature was low (one on a night dive and one in Catalina Island off California coast). I was cold and felt my sinus was blocked. I tried blowing while holding my nose, swallowing (or pretending to swallow) to clear but just can't. Once a while, I will have sinus problems on land during cold winter days. Has this happened to you before - you can clear fine in warm water but have trouble in cold water? Thanks!