I've tried a few different methods with varrying results.
One thing you can do to focus your energy elsewhere is to reconstruct your day, or the previous day if your doing it in the morning. Slowly think through every detail of the day from the time you got up to the time your holding your breath. It's amazing how long that can take especially if your really focused on recalling each detail.
The other method I've used more recently is trying to visualize my dives. I'm usually diving at the same spot on each weekend so I can recall fairly well what the conditions are like and what the environment is. On each breathhold I try to visualize myself going further, deeper and really experiencing the dive. I find its useful to mentally prepare for the dive so that when I get in the water the diving is automatic. However, some people of talked to find that the visualization of being underwater where they can't get air makes them focus more on being uncomfortable. To each their own!
the third technique you can use to release tension is to focus your mind on each individual body part. Start by focusing your attention on your feet and will them to relax sometimes a brief tensing of the muscle follwed by a complete release will help. Run through every muscle group until you feel tottally at ease (and your five minute breath hold has elapsed
)
Hope that helps...
