Do dive tables or dive computers themselves protect you? No, they are the best guidelines that we have today if we fit into the normal parameters of a diver. What if we put ourselves outside the normal parameters? We trust our training and our equipment but we still have far to go. Let me explain. 

DCS or Decompression Sickness and how it happens to a diver, is a moving target. It is not exact in how it happens for every diver. Yet, you can look at a dive table and assume you would be completely safe if you follow them. And yes, mostly that is true. However there are consistent emergencies in the dive world that are within the table and computer guidelines. 

I could scare you with stories of permanent paralysis, traumatic brain injuries, and death. My goal is to get you to pay attention rather than be afraid. The science and study of DCS is largely done in case studies after the emergency is over. Difficult to know when it is going to happen and dangerous to create it on purpose. Consequently, the dive medical community is still figuring out why some cases happen even though they were in safe limits. 

Medical conditions like diabetes, high blood pressure, and medications like blood thinners, insulin, and age, physical condition, can affect a divers condition outside what is considered normal. Self inflicted changes like pushing the boundaries of depth, shorter surface intervals, too many multiple dives, excessive drinking alcohol, all can play a part. Many divers say they didn't believe it would happen to them. So they just didn't prepare as cautiously as they should have. My point is pay attention. 

Stay conservative always is a good rule of thumb. If you have any conditions then you can do some research rather than waiting until a problem happens.

I dove with a buddy at the exact same depth levels, same time underwater, same # of dives. We both have diabetes and both take insulin. Younger and in overall better health than I was, this person was in better physical condition. We were within the safe parameters and guidelines of the dive tables. Both had modern dive computers and we both dove a safe profile and did a safety stop. 

So why did my dive buddy get DCS and I didn't? Alcohol! 

Too much of it the nights before diving. Not only was it a lot of sugar but it thins the blood and dehydrates the diver. So you might have got hammered and dove the next day and nothing happened. Great, I am happy for you. Will it be the same next time or when you are older. This has nothing to do with drinking but to pay attention and be aware of those things that can take you out of the normal category. 

Maybe you are so exhausted that you shouldn't go. Maybe you are cold, low blood sugar, high blood sugar, your computer went into the red or very close on a previous dive, the air in your tank has a light odor but you don't want to cause problems. 

I could continue but I think you get the point. Be aware, pay attention and make decisions. Failure is not an option here. Your success is all I am after. Be a better diver.