30 ft is the classic failure point for equalization, it certainly was for me, and I have seen many others with the same problem since. you are probably using Vasalva. Tips:
- learn frenzel, look for the videos and tutorials on this site
- read these definitions and watch the great video on this site:
Doc's Diving Medicine Home Page
- keep your head in a neutral position (don't strain to look down at the bottom)
good luck
