Right bundle branch block of the heart and Diving

I wonder if you would be kind enough to give me a simple explanation for the term "RBBB".
My son underwent a diving medical today and the result of the ECG showed he had a "RBBB" He is 14. The Doctor passed him "Fit to Dive" and said that quite a few people are born with that condition.

RBBB stands for Right Bundle Branch Block, a frequent benign minor alteration of the conduction of the electrical stimulus along the heart walls, by which the stimulus to the right ventricle is slightly retarded and a specific kind of wave is detectable with the EKG.
This condition is hardly considered a disease, but almost an innocent variation from normality, is relatively common and frequently congenital. It normally does not affect normal cardiac performance at all and is fully compatible with a normal life and even strenuous activities.