Simply put, an unrepaired inguinal (groin-area) hernia contraindicates scuba diving. Without repair, theoretically, part of the small intestine could push its way through the inguinal canal during the normal strain and effort of lifting equipment. This small loop of bowel can then become trapped within the inguinal canal.
This can occur because the gas normally found inside the small intestine expands as the diver ascends, and the pressure exerted by the expanding gas volume will then hold the bowel in place and not allow it to return the abdominal cavity. Although symptoms may start out mild (such as pain, or scrotal and testicular pressure in men, noticeable whenever one tries to lift or walk), a medical emergency can result if the loop of bowel is not released.
Once your doctor repairs the condition and releases you to full activity, you should be able to return to diving if you are able to perform your normal exercise and activities without symptoms.