Deep Molasses Reef, Key Largo: A Closer Look

by | Jul 25, 2017


The following is an excerpt from Tim Grollimund’s ebook: “The Less Traveled Reef: Going Deep Reveals Abundant and Unusual Sealife.”


Needless to say, reef diving here is a real treat, since almost everything is shallow.  But there are a few places in the outer edges of the reefs that are a whole different world.  If you look on the map of dive sites for the Upper Keys area, you will see some mooring balls near or just outside the Sanctuary Preservation Area lines.  You can find the maps at

Deep French, Deep Elbow and Deep Molasses are quite different than their shallower namesakes.  I am happy to drop in on any of them – in no particular order – just depends on the day.  The contours begin around 50 feet, and usually we stay in the 70 to 90 foot range.  Nitrox is the preferred gas on these dives, and we usually use a mix of 32 or 36 percent.  The current, of course, will dictate which bearing we take from the mooring ball.


Once you are down the line the first thing you notice is the abundance and variety of tube and barrel sponges.  There is a very different feel to these dives, and I would encourage you, if you have a boat full of advanced or higher level divers, to give these sites a try.  Again, these dives are not for beginners. These are advanced dives.  We have done them as drift dives as well.  The perfect scenario would be a sixpack operator or private boat with experienced dive buddies.

Is is quite common on the ledges to see eagle rays, loggerhead or hawksbill turtles, schools of horse eye jacks, and schools of spadefish.  Typically we descend to our maximum depth range for the first half of the dive, and work our way back up the slope on the way back.



A few weeks ago we had a very unusual sighting – a group of over two dozen Atlantic Devilrays.  They have a profile that looks like a giant manta ray, but are considerably smaller and appeared to be more brownish in color.  They also move quite swiftly.  Look on page 460 of The Reef Fish Identification book for Florida Caribbean Bahamas (3rd edition) and you will see a small reference to Mobula hypostoma.  Uncommon, to say the least, since the International Union for Conservation of Nature Red List entry specifies the Mobula as “Data Deficient” – meaning there is not enough information on abundance or distribution to make an assessment as to whether this is a threatened species under their current methodology.



Longsnout Butterflyfish, found only in deep water


Go to: and put Mobula hypostoma in the search box. Great summary here, and a wonderful resource for you to have in your list of reference materials.

Another great feature of the deep sites is the abundance of angel fishes – all different types, from juveniles to quite large specimens.  Queen, blue, gray, french and lots of rock beauties, many times in groups of 3 to 5, seem quite comfortable with us gliding through the barrel sponges and sea fans.  We also see some unusual hamlets – shy and indigo hamlets – but they are very reclusive and take a fair amount of time to approach and frame for a decent image.

Tim Grollimund is based in Key Largo, Florida. He wrote the scuba diving column for the local newspaper for several years, and also served as a Working Group member and Alternate Representative on the Florida Keys National Marine Sanctuary Advisory Council.  The ebooks cover a wide range of marine life and reef conservation topics. See for the ebook collection.

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