Blue Hole, near Andros Island, Bahamas
July 30, 1999
is a short description of a short trimix cave dive in a Bahamas Blue
Hole called Donut Blue Hole. This cave is just offshore of Andros Island,
a 40 minute boat ride from New Providence. Boat and mixes were provided
by DiveDiveDive. Diving the cave was Paul Christman
Paul was to enter the cave as a solo diver; Joel and I were a buddy
The depth of the cave was unknown to us, but was guessed to be in the
360fsw range. Due to logistical problems, Joel and I decided the entire
dive, including deco, should last only about 70 minutes. All depth/mix/deco
calculations were adjusted for that outcome. A lot of flexibility was
also calculated in. Our target depth was 210fsw, but we had enough room
in the mix and deco process to bounce to 240fsw if we wanted. Paul's
mix would allow him to go much deeper, down to 320fsw.
The entry was from a roll off the boat. I was taking my video camera,
so I got all set before I started breathing my gas. Nitrox 50 -- for
deco after the dive -- was carried as a stage, and was to be dropped
at any convenient ledge. Pure O2 was hung from the 20-foot down line
below the boat. Water temp was 85-degrees F, and the cave water was
not expected to be much cooler.
I knew I had more Nitrox 50 than I could ever use, so I started breathing
it on the drop into the blue hole. At 50-fsw, I switched to my 17/35
The blue hole has a flat, sandy area in the middle, at about 40 fsw,
surrounded by a circular depression, as if some giant had pressed a
donut into the coral, leaving a giant impression of a donut. On one
side of this hole was a large crack, about 15-feet wide, about 40-feet
long, which opened into a much larger cavern.
While not a cavern dive, light from the sun could be seen from most
parts of this cave, especially if you stayed by the line.
We tied off the primary reel at about 120-feet and dropped almost straight
down. At about 190-feet, we could see the permanent line, and we tied
off. The permanent line and the walls were covered with a white, slimy
bacteria culture. It was so thick that our bubbles dislodged it wherever
they hit it, and the result was very similar to ceiling/silt percolation.
My video showed little else but these globules of bacteria. There was
virtually no life at all in the cave, so I imagine that the bacteria
used up all the oxygen in the water (that's just a guess). Excluding
the bacteria, there seemed to be only a little silt on the horizontal
The cave was not "tidal"... there seemed to be no flow at
The permanent line angled down just slightly below the horizontal, starting
at the 190-foot tie off and ending at about 200' feet of penetration
and 210-fsw depth; at that point, the line took a sharp turn straight
down. Paul had preceded us into the cave and was already about 50feet
below us and was continuing down.
I swam around the cave, staying near a wall since, without it, my video
camera would have nothing to focus on. The room was quite large, maybe
80 feet by 40 feet, and huge limestone boulders sat wedged in gargantuan
cracks. After swimming about 50 feet away from the line, I looked down
and could see Paul ascending. I swam back to the line and dropped down
a bit, following Joel into the abyss. We both stopped our descent at
I had brought along a Scuba Pro sonar depth gauge and pointed it straight
down. The reading showed "30 feet". I couldn't see 30 feet
down -- the bubbles from Paul and the bacteria globules were making
it tough -- but I felt sure it was deeper than that. Later, Paul confirmed
that the hole bottomed out at 265fsw, so the depth finder was correct.
Our "turn" was upon us, so we slowly ascended and retrieved
the reel at 190fsw. We stopped at 120fsw for our first deep stop. We
retrieved our Nitrox 50 bottles and started breathing them at 60 feet.
The remainder of the deco stops were uneventful. While we were at the
20-foot stop, hanging like limp dolls on the line, several black-tipped
reef sharks came over to investigate, but we weren't on their menu for
Dive time including deco was 72 minutes.
Although there wasn't much to see except the bacteria, it was a fascinating
(Photos to follow later.)