Put simply - As dangerous as the diver concerned allows it to be.
If a diver follows the basic safety recommendations provided during the course of their entry-level training, then there's little that can go wrong for them. In the unlikely event that something does go wrong, then there's little that they won't have the skills, knowledge and capability to resolve safely.
Accidents only tend to happen when divers become complacent or arrogant enough to ignore the basic safety recommendations - or if they allow their core skills to perish through inattention and lack of practice.
Prudent safety recommendations/advice include:
- Plan your dive and dive your plan (gas, depth, time, navigation and contingency plans for the worst-case scenarios)
- Fully apply the training you have received, no excuses.
- Dive conservatively and within your own personal comfort zone.
- Dive within the limits of your training and experience
- Maintain and confirm your medical fitness to dive
- Continually practice and refine emergency/contingency procedures
- Don't undertake decompression, overhead (cave/wreck) or solo dives without specialized training.
- Adhere diligently to the buddy system as a fail-safe for emergencies.
- Maintain situational awareness of your gas, depth, time, no-deco limit and your buddy.
- Retain a healthy reserve of air to cover all contingencies.
- Be prepared to abort any dive, at any time, for any reason, if you don't feel comfortable.
- Don't succumb to peer pressure or ego-driven decision making when determining what you are comfortable to undertake.
- You are only as good as your last dive, or your last skill practice - respect the importance of frequency and cumulative experience on your diving performance.
- Plan and prepare to cope with the worst-case scenario. Don't make safety assessments in the assumption that everything will always go right.
- Understand your capabilities and how they relate to the dives you plan to undertake.
- Don't do 'trust me' dives - where you rely on the skills, experience or capabilities of another diver to ensure your own safety.
Scuba Divers die ... in the Blue Hole of Dahab