Stretching! I am a Registered Nurse in a hospital, and my PT department conveys to me that 70% of mobility and flexibility involves stretching and mobility... NOT necessarily brute strength. How many of you have had a nasty muscle spasm while suited up or making a quick move underwater?
Yes, obesity while diving is downright dangerous due to airway and cardiac issues. My opinion is "extreme" workouts are NOT the way to go but staying in shape with moderate cardio will do you just fine for diving. All about the stretching, mobility, and flexibility.