Semi-Cave: Is this dangerous?

[Boyan]

Hi,

I have 8 dives under my belt, so pretty new to the game.

After doing my CMAS 1* a year back I did 4 more dives while on vacation two weeks ago.

I was surprised to be offered "cave diving" with my lack of cave certification in the dive shop in greece. I told them I am not interested in cave diving, but at the end we still ended up on the cave dive, fortunately it wasn't serious cave diving. We did a reef dive followed by "volcano diving", basically diving between large rocks with some overhead action as well. The "caves" were basically short passages or tunnels, maybe 10m swimming in real overhead environment. Most of the time we were surrounded by rock walls, but still with access to the surface, although it seemed very narrow.

We even had some first time divers within the group. The caves were as I mentioned pretty short, no lights needed, just 5-10m of cave maybe, but still overhead.

Is something like this dangerous for OW divers and if yes why?

While I realise the dangers of serious cave diving, is something like this dangerous?

The depth was about 10 meters (+-30 feet).

 

[BoltSnap]

It sounds more like a short passage or tunnel not a cave. I have seen it done in many places with beginner divers no issues (I am not making a judgement here about if it is right or wrong, just stating that it is a regular occurrence).

 

[The Chairman]

This is probably a language thing. I have dove such "caves" around the Socorro Islands. Not a big deal at all. Just know your limitations and don't exceed them. IOW, if you feel nervous, just thumb the dive.

 

[beester]

A "semi cave" (like in still daylight penetration and not a lot of penetration (10m), multiple exits) is save, as long as you are comfortable and call the dive if you feel not at ease.

However there are a lot of "sea caves" which are promoted as easy enough, but can pose risks.

Four dead in Italian cave

 

[Neilwood]

I think you have to look at each overhead environment on its own merits. If you are in a hard floored semi cave with plenty of light and minimal penetration, I don't think it would be too dangerous. However it is easy to go from that to a similar looking semi cave with silty floors that becomes an issue

One of the issues I have with the situation the OP presents though is that brand new OW divers might not have the experience or confidence to thumb a dive if they aren't happy (particularly in a group of more experienced divers the "we have done this hundreds of times so you will be fine" attitude can be prevalent).

One thing to remember is it doesn't matter how good a diver you are or how comfortable you are, it is the divers around you that could cause the problem. If one panics in an overhead or kicks up the silt, are you confident you can get out?

 

[Boyan]

It was indeed a very easy dive, in fact my most pleasant dive so far with very little variation in the depth. There was silt, but it didn't go very high when kicked up. The "we know what we are doing" attitude was pretty strong. We were advised to not look at our gauges and just let the instructor handle these things lol. I felt safe and Im not complaining, but while swimming through the tunnel, I thought, isn't this exactly the type of situation the internet has always warned me about? I decided to enroll in more serious class, so just in case Im prepared for any surprises like that.

 

[Jack Hammer]

IMO, the problem with dives like this is even if it were to be perfectly safe, when it gets promoted as something more advanced and super easy it can leave divers thinking that it's perfectly safe and super easy to enter any overhead or cave environment.

 

[Doppler]

Jeff has pointed out the one huge drawback of this type of dive... a little touch of the Normalization of Deviance. And of course the often used blanket statement meted out on the public forums is that an overhead is an overhead and unless cave trained, stay out. However, the treatment of a simple swim-through as described in the original post as verbotten does its own type of damage. Open-water divers conduct this type of dive everyday and the short passages where these dives take place are not littered with dead divers. The louder and more often we cry wolf, the less believable our warnings concerning steering clear of true overhead environment dives become. One needs to be careful, but a swim-through can be a fun experience that helps to build one's skillset. A benchmark might be that if you need a light to see details such as invertebrates living in there, it's more than a swim-through.

All in all, the best advice offered from the posts above is that if you feel iffy about doing the dive, any dive, thumb it.

 

[Neilwood]

It was indeed a very easy dive, in fact my most pleasant dive so far with very little variation in the depth. There was silt, but it didn't go very high when kicked up. The "we know what we are doing" attitude was pretty strong. We were advised to not look at our gauges and just let the instructor handle these things lol. I felt safe and Im not complaining, but while swimming through the tunnel, I thought, isn't this exactly the type of situation the internet has always warned me about? I decided to enroll in more serious class, so just in case Im prepared for any surprises like that.

I really hate seeing the bolded sections - that fills me with dread.

First - the silt. someone kicks a bit too hard and you have a silt out with zero vis. Not a great deal if there is a current and you are willing to wait it out without panic.
Second - The "we know what we are doing"- do they really know what they are doing or are they simply getting away with bad habits while all the time heading to the major screwup that kills someone?
Third - always look at your gauges. You and only you are responsible for your own safety. What happens if you run out of gas mid passage due to not watching your gauges? I dread to think.
Fourth - I wonder if the instructor has sufficient training to know what is dangerous and why. If I did this with an experienced cavern/cave diver I would feel a lot safer than an instructor with no training in overheads - the experienced cavern/cave diver will be able to spot and plan for any dangers whereas the instructor could be oblivious to them.

Do they have a plan for what happens if a diver gets into difficulty during a passage or are they simply "never had any issues so why worry"?

 

[Reku]

One thing to remember is it doesn't matter how good a diver you are or how comfortable you are, it is the divers around you that could cause the problem. If one panics in an overhead or kicks up the silt, are you confident you can get out?

This is the take away from this thread for the most part. Even in an overhead environment with two open ends things can go south fast.

I was once in a quarry with a concrete tunnel at 90ft about 60' long, 15' wide - nothing too serious right? Well the people in front and behind me silted out the entire thing while I was inside. Suddenly 15' across felt like eternity - you couldn't tell the difference between going down the tunnel and going across the tunnel.

This tunnel did not have a guideline running through it.

If someone without much overhead experience were to encounter something similar it would probably be a death sentence.

All overhead environments regardless of size have the potential to kill you if you panic.

Stay Calm, Stay Alive - think about everything 1 step at a time.

1. Am I still facing the same direction that I was when the silt happened?
2. Where is the wall?
3. How far have I traveled into the tunnel?


Yes I am still facing the same direction - the tunnel runs east to west and I am heading west - good.

If I go to my left I should run into a wall. Ok - found the wall.

Now I need to keep moving west and I'll be out in about 30ft.


Generally if I do anything even semi overhead - I bring a map/blueprint of the structure.