Little Cayman giants abound in ‘Sponge Belt’

Steve Reichenbach, centre, with fellow divers Gary Lemme, right, and Woody Alpern.

The crew from Divetech and a group of divers returned to Grand Cayman Saturday after exploring the depths of Little Cayman.

Some 42 divers and instructors, taking part in Divetech’s 15th annual Innerspace event on 18-25 May, dropped as deep as 330 feet and spent as long as three hours underwater on each dive.

At those depths, the terrain is considerably different from what recreational divers, who can go to a maximum depth of 130 feet on a tank of air, see on their dives.

Drew McArthur, a Divetech instructor who led the deepest dives during Innerspace, said, “It was the sponges that blew my mind … they were fascinating.”

He described what is called the ‘Sponge Belt’, which appears at about 200 feet. “Coral we normally see at the 40 to 100 feet depths die out, they cannot live down there. The habitat changes; the abundant coral disappears and it leaves open ground for sponges to thrive. The sponges we found in the Sponge Belt were absolutely mammoth.

“Some of the barrel sponges were big enough to fit a diver with tanks and rebreather. They could swim inside them. And the elephant ear sponges were gargantuan.”

He was so taken with the sponges on the deep wall at Little Cayman that he missed at least one exciting encounter.

Dirk Peterson checks out a giant sponge during an Innerspace deep dive on Little Cayman’s Bloody Bay Wall. – Photo: Drew McArthur, Divetech

“One day I was staring at a sponge and all the different formations of it, and didn’t even notice a hammerhead shark swimming right behind me,” he said. “I missed the hammerhead completely because I was looking at the sponge.”

Since McArthur was also acting as the photographer on the dive, he had reason to be peeved. However, there were other opportunities to see and photograph plenty of sharks and other wildlife on the multiple dives. “There were a lot of sharks throughout the week, mainly reef sharks, and a couple of hammerheads,” he said, as well as a large number of a green sea turtles.

The divers broke into three groups for the week, with one group diving to about 140 feet on air, but using rebreathers; another going to 200 feet on Normoxic Trimix with Divetech owner Joanna Mikutowicz; and the third group dropping to about 330 feet with McArthur on Hypoxic Trimix.

A group of Innerspace divers approach a giant barrel sponge. – Photos: Drew McArthur, Divetech

Unlike with conventional scuba gear where divers breathe in air from the tank on their back through the mouthpiece and breathe out exhaled air in the form of bubbles, rebreathers allow the divers to breathe their own air over and over again, and produce no bubbles.

The divers use Trimix, a mixture of oxygen, air and helium, to reach the depths that cannot be reached with the use of normal air tanks or nitrogen-oxygen mixes. Adding helium to the mix reduces the risk of nitrogen narcosis while doing deep dives, and as oxygen can become toxic at deep depth, it is replaced with helium.

At depths of 200 and 300 feet, the light begins to fade and the dive is reminiscent of a night dive, McArthur said.

Steve Reichenbach takes a look at another of Little Cayman’s giant sponges.

He said there were also “layers” at 200 and 300 feet. “The wall cascades and drops down, and there is a ledge where you can drop down a level”, he said. “It is notable at 200 feet and another 100 feet below at 300. Each one seems to have a thermocline, which means the water gets a little bit colder, and it gets noticeably darker.”

For the divers, the vast majority of whom were visitors, the most attractive thing about taking part in Innerspace this year was being able to explore a part of the underwater world of Little Cayman where “arguably no one has ever been before”, McArthur said.

Getting all the equipment, tanks, rebreathers and gases to Little Cayman was a logistically complicated operation that took months of planning and implementation. Some of the equipment was shipped over by barge, while Cayman Airways delivered the rest to the island. Much of the gases needed for the dives are not available on Little Cayman, so the Divetech crew had to make sure they had everything they needed before the Innerspace dives began.

Divers on the Hypoxic Trimix dive descend.

One extra complication is a worldwide shortage of helium, McArthur explained.

“The helium we use to make Trimix, there is a limited supply. People have been saying for years and years that helium for divers will run out soon,” he said.

A few months ago, Divetech put in an order for 15 large canisters of helium for Innerspace from its supplier, but was told none was available. After some negotiations and “panicking” because the spaces for the event were pre-sold, McArthur said, “instead of 15 [canisters], they could get us five a month”.

Next, that pure helium had to be mixed with the other gases to make the Trimix. “Our concern was, if we messed it, there would be no helium left to correct it,” McArthur said.

John Strang rounds a coral outcrop on Bloody Bay Wall.

It all worked out well in the end, although the “preparation work to get all this to happen was colossal – a lot of sleepless nights and gray hairs”, he said.

The team worked with Reef Divers in Little Cayman on the event, and the divers were transported to the dive sites on Reef Divers boats. “They were incredibly supportive and helpful,” McArthur said.

The team is already thinking about next year’s event.


  1. Amazing logistics, awesome looking dives and a apparently seemless operation. Good effort Divetech! I am curious where the gas comes from to inflate the wing when you only use a wetsuit? (I’ve never done warm water CCR while OC wing inflate is easy – back gas).

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