Santa Rosa Blue Hole, Another collapse?

[jstotz]

Out of curiosity, were there any rumors of people getting through the grate before the May collapse or is it still assumed that no one has entered since Mike Young and Shane in 2016?

 

[jengineer61]

I dove The Blue Hole in 1997. The flow was strong at that time and you could find places along the wall where the flow was coming from. Kinda cool fro my 357th dive. There was a grate over the entrance to the cave system along with a sign.

 

[jstotz]

I dove The Blue Hole in 1997. The flow was strong at that time and you could find places along the wall where the flow was coming from. Kinda cool fro my 357th dive. There was a grate over the entrance to the cave system along with a sign.

I read that the cave entrance was sealed off with a grate even since 1976, due to a double fatality that year of a couple of open-water students who deviated from their training dives. For years this grate took the form of a periscope-shaped metal tube about 3ft in diameter with a 90 degree bend, known as the snorkel.

In 2016 Mike Young and his safety diver Shane Thompson were given permission to map the cave system. They reported that it continues to go very deep very quickly and gets very small and mazy consisting of large breakdown. This expedition famously ended with Shane's death due, in short, to a deviation from the agreed-upon dive plan, getting stuck with a large backmounted rebreather, and subsequent panic.

At some point in recent years, possibly due to damage from a collapse, the snorkel was replaced with a large flat grate of tubular metal bars.

In October of 2024 it appeared to me that a very irresponsible and rule-breaking diver might be able to de-rig and get around the grate or even lift the entire grate.

In May of 2025 a very large boulder fell on top of the grate and probably remains a welcome layer of additional security by administration.

The cave system is considered deadly due to depth and the tightness of the breakdown maze. The entire system is apparently unstable as you hear about collapses almost yearly. Strange that it was sealed after only two deaths in 1976.

I was curious if anyone had been in since 2016.

I welcome any corrections, additional info, and the usual paternalistic warnings.

 

[boulderjohn]

In 2016 Mike Young and his safety diver Shane Thompson were given permission to map the cave system.

Mike and Shane were part of a team (ADM) headed by Curt Bowen. The cave had been opened a year before by an earlier team led by Bowen. This team was charged with both exploration of the deeper parts of the cave and opening up the upper parts to make it more accessible.

Mike and Shane were the forward exploration team. They were a diving team--Shane was not Mike's safety diver. They were the only ones who ever got past the first major restriction. Without giving it a lot of thought, I would say about 7 other divers worked above that restriction. On the day Shane died, the schedule was for Mike and Shane to explore first, then a team would work on that restriction, then another team would work at the upper level. If multiple teams worked at once, it would risk raining rocks and a potential sealing avalanche upon those below.

Mike determined that the cave ended at his furthest exploration, so there was no point in continuing. (That was immediately before the incident with Shane.) Even if it had been a reasonable cave system, it would have required very highly trained cave divers. The cave was therefore sealed. The problem was that the work that had been done to open up the upper levels had dramatically widened the opening, and that opening had a lot of loose rock that kept collapsing. The grates that had originally covered it all just fine were now too small.

No one has been in the cave since Shane's body was recovered.

 

[jstotz]

Mike and Shane were part of a team (ADM) headed by Curt Bowen. The cave had been opened a year before by an earlier team led by Bowen. This team was charged with both exploration of the deeper parts of the cave and opening up the upper parts to make it more accessible.

Mike and Shane were the forward exploration team. They were a diving team--Shane was not Mike's safety diver. They were the only ones who ever got past the first major restriction. Without giving it a lot of thought, I would say about 7 other divers worked above that restriction. On the day Shane died, the schedule was for Mike and Shane to explore first, then a team would work on that restriction, then another team would work at the upper level. If multiple teams worked at once, it would risk raining rocks and a potential sealing avalanche upon those below.

Mike determined that the cave ended at his furthest exploration, so there was no point in continuing. (That was immediately before the incident with Shane.) Even if it had been a reasonable cave system, it would have required very highly trained cave divers. The cave was therefore sealed. The problem was that the work that had been done to open up the upper levels had dramatically widened the opening, and that opening had a lot of loose rock that kept collapsing. The grates that had originally covered it all just fine were now too small.

No one has been in the cave since Shane's body was recovered.

I've read at least a couple accounts of open circuit bubbles causing near fatal collapses during dives down there, particularly during the 1976 recovery.

In the unlikely event that it were to ever be reopened it sounds like a closed circuit rebreather would be mandatory?

 

[VikingDives]

At some point in recent years, possibly due to damage from a collapse, the snorkel was replaced with a large flat grate of tubular metal bars.

In October of 2024 it appeared to me that a very irresponsible and rule-breaking diver might be able to de-rig and get around the grate or even lift the entire grate.

In May of 2025 a very large boulder fell on top of the grate and probably remains a welcome layer of additional security by administration.

The cave system is considered deadly due to depth and the tightness of the breakdown maze. The entire system is apparently unstable as you hear about collapses almost yearly. Strange that it was sealed after only two deaths in 1976.

I was curious if anyone had been in since 2016.

I welcome any corrections, additional info, and the usual paternalistic warnings.

I've posted this elsewhere, but the snorkel was removed because there was a kind of wrought iron grate behind it, that caused water to flow in a manner that was making the cave entrance larger. There was no collapse damage. The reason the snorkel was removed was that there was evidence of someone going into the cave or at least into the entrance. Also, the opening on the side of the grate was getting larger.

It was replaced with the current grate around April 2024. There was a collapse on the north wall within about 6 weeks, but that was opposite the grate. So the entrance was unaffected. The grate weighs about 600 lbs in the water, so it was in the realm of possibility that someone could have moved the grate, but they weren't going to move it far without liftbags.

This year, a collapse happened above the grate, and there is a 20x6x6 ish rock on top of the grate now. There is no way to access anything unless that rock is moved.

There's more information here: The Great Blue Hole Grate Installation Project - Viking Dives

and there's current video of the grate here: If you jump forward to about 3:00 you'll see the grate.

The dark gray rocks on the walls are clay, which appears at last year's collapse as well as this year's. The clay is really soft, and is probably the reason that the walls collapse.

Interesting to me is that the collapse on the north wall happened about 6 weeks (IIRC) after we installed the snorkel, and the place where the collapse was centered was right under where they parked the crane the pulled the snorkel out.

Two days prior to the most recent collapse, Santa Rosa lowered the water level at BH by about 4 feet to make some repairs to the handrails at the steps.

There's a thread about the first collapse here: Blue Hole NM Collapse?

 

[boulderjohn]

I've read at least a couple accounts of open circuit bubbles causing near fatal collapses during dives down there, particularly during the 1976 recovery.

In the unlikely event that it were to ever be reopened it sounds like a closed circuit rebreather would be mandatory?

There was no problem with open circuit bubbles. First of all, most people on the team were on rebreathers, including all the people doing the deepest work. Next, the problem was that the army corps of engineers had tried to fill the cave opening with tons of loose rock, and the path through all of that was very narrow. When we started, the top 10-12 feet was very tight and very vertical before turning into a steep slope down to (IIRC) about 140 feet before the first restriction. The problems involved that loose rock, which was mixed with a fine, gray clay silt. Just getting through the upper portion dislodged rocks, and any movement at all created a siltout. Working to enlarge the upper levels required moving rocks in a Braille environment.

To give you an idea, I was working in the upper area in a moderate siltout when the siltout became total. I wasn't worried--the flow would clean it up if I held still. In the silt I saw a Shearwater computer, but I could not see the arm to which it was attached. It was Shane's. He and Mike were returning from the depths and had brought their total silt environment with them. Mike had already passed me without my knowing it, and there was only room for a couple people in that room.

At the end of the day before the incident, Mike asked about getting rid of some of the upper débris to make their entry safer, and we decided that I would go in solo and open the upper level as much as possible. I had a deadline for exiting so they would know if they needed to go in to help me. I worked up until that deadline moving rocks and creating as little silt as possible, and then I went full on destruction. I looked up at the light from the exit, dug both arms in as deeply as I could in front of me, and threw the silt and loose rocks behind me. I did that again and again, working my way up to the light. Eventually I reached and got nothing--I was completely out of the cave, but all I could see was still a faint glow above me.