I admit I have done few such dives myself. Here is a list of what people dive here (Chania/Crete/Greece) practically every single day for the summer season
- The most popular local dive (called Cathedral) is a cavern accessible even to OW divers. The entrance is at a depth of 45feet, then is an overhead section of about 30 feet long and then the "cavern" opens up to a big chamber with collapsed roof hence plenty of natural light. One can surface in the cavern if needed. Entrance tunnel is very wide (it would fit 3 maybe more divers going in side by side or on top of each other). No lights are usually used here (plenty of natural lights)
- Another cave very popular even to OW divers (called Elephant Cave) is this one: Entrance at 40feet/12m, then a 30feet long overhead section and then a huge (~600 feet long) shallow (~4feet - divers actually walk around) chamber filled with breathable air and very nice rock formations. Lights for this dive is a must as the main chamber has no natural light.
Local dive stores would bring to those two any OW that feels comfortable about it day in and day out for about 6 months every year.
Then there are slightly more advanced caves or swim throughs.
- One (called Seal cave) has entrance at a depth of about 50feet and then gradually after a length of about ~300 feet it reaches the surface where a chamber filled with breathable air is. The tunnel is rocky and there are no dead ends in the tunnel which is wide enough for 2 divers to dive side by side comfortably. Obviously lights is a must here too - interestingly they don't use a cave line.
And the list goes on with more and more challenging sites. LDS usually bring to these sites only people who have dived with them before and seem to be "advanced" enough.
Generally visibility here is very good (even better inside the caves) and there are zero currents. There are few sandy patches here and there in these caves/caverns but the sand is "heavy" and doesn't silt. At the caves mentioned above, there are no narrow passages that wouldn't fit at least 2 divers diving comfortably side by side neither dead ends etc.
The main local dive store do these dives usually with 3 guides (at least 1 or 2 instructors and 1 or 2 DM) for a group of up to 8 divers (less for the more advanced caves). One guide is leading and two at the back are watching. Should a diver feel uncomfortable going in the cavern/cave he/she can wait outside with the 3rd guide. Smaller dive stores do these with fewer guides - I've seen even with just one guide for 4-5 divers (or even more that I haven't seen).
I am not advertising this practice as safe and clearly these conditions cannot be generalized. I am just describing what is happening here regularly. 100s of divers do such dives every year (here and I am pretty sure elsewhere). I admit I have done these dives and even worst I did them when I was a quite new divers because that's where LDS bring divers and that's what everybody was doing around here. Now I am more into macro phorography and as I don't find caves attractive enough I ended up diving on "easy" shore dives mostly by myself.
- The most popular local dive (called Cathedral) is a cavern accessible even to OW divers. The entrance is at a depth of 45feet, then is an overhead section of about 30 feet long and then the "cavern" opens up to a big chamber with collapsed roof hence plenty of natural light. One can surface in the cavern if needed. Entrance tunnel is very wide (it would fit 3 maybe more divers going in side by side or on top of each other). No lights are usually used here (plenty of natural lights)
- Another cave very popular even to OW divers (called Elephant Cave) is this one: Entrance at 40feet/12m, then a 30feet long overhead section and then a huge (~600 feet long) shallow (~4feet - divers actually walk around) chamber filled with breathable air and very nice rock formations. Lights for this dive is a must as the main chamber has no natural light.
Local dive stores would bring to those two any OW that feels comfortable about it day in and day out for about 6 months every year.
Then there are slightly more advanced caves or swim throughs.
- One (called Seal cave) has entrance at a depth of about 50feet and then gradually after a length of about ~300 feet it reaches the surface where a chamber filled with breathable air is. The tunnel is rocky and there are no dead ends in the tunnel which is wide enough for 2 divers to dive side by side comfortably. Obviously lights is a must here too - interestingly they don't use a cave line.
And the list goes on with more and more challenging sites. LDS usually bring to these sites only people who have dived with them before and seem to be "advanced" enough.
Generally visibility here is very good (even better inside the caves) and there are zero currents. There are few sandy patches here and there in these caves/caverns but the sand is "heavy" and doesn't silt. At the caves mentioned above, there are no narrow passages that wouldn't fit at least 2 divers diving comfortably side by side neither dead ends etc.
The main local dive store do these dives usually with 3 guides (at least 1 or 2 instructors and 1 or 2 DM) for a group of up to 8 divers (less for the more advanced caves). One guide is leading and two at the back are watching. Should a diver feel uncomfortable going in the cavern/cave he/she can wait outside with the 3rd guide. Smaller dive stores do these with fewer guides - I've seen even with just one guide for 4-5 divers (or even more that I haven't seen).
I am not advertising this practice as safe and clearly these conditions cannot be generalized. I am just describing what is happening here regularly. 100s of divers do such dives every year (here and I am pretty sure elsewhere). I admit I have done these dives and even worst I did them when I was a quite new divers because that's where LDS bring divers and that's what everybody was doing around here. Now I am more into macro phorography and as I don't find caves attractive enough I ended up diving on "easy" shore dives mostly by myself.