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Gearing Up

But the divers didn't just want to go to the bottom. They need to be able to move up and down in the water column, over the topography of the lake bottom, and in the end, to get back up to the surface. In other words, they needed to have buoyancy control. Valves on the dry suits that let the divers pump air into and out of the suits, give them that.

When descending, they let air out of their suits to increase their density. This helped them sink. Conversely, when they wanted to ascend, they typically pumped air in. But it got trickier near the surface. As the pressure of the water column above the divers decreased, the volume of the air expanded. This could have increased their buoyancy too quickly and caused them to shoot up. So, when surfacing, the divers actually let air out. "Ascending slowly - and descending slowly for that matter - is key", emphasizes Maria. The human body has quite a few air spaces, such as eardrums, and they need to be equalized with water pressure to prevent damage. "Good buoyancy control using the valves is something that dry suit divers practice constantly", notes Ian. "After getting all geared up and standing around for five minutes in multiple superinsulating layers with a 40-pound vest and a ten-pound helmet on that strains your neck muscles just to keep your head upright, being in an icy cold, pretty much weightless environment started to seem like a good idea", says Maria. "To enter the lake, divers sat at the edge of a three- to four-foot diameter hole they had melted into the ice previously. Since the lake water filled the hole pretty much up to the surface, the divers could just lower themselves gently into the water", explains Ian.

Ian with all his dive gear on

"They let a bit of air out of the suit and slowly sank. To get below the 15 feet of ice in Lake Hoare typically took a minute or so and to get to the lake bottom at an average depth of 35 feet took an additional three to five minutes", says Donna.

"Once on the bottom, it was important to regulate your movements", notes Ian (more buoyancy control!).

The benthic mats grow slowly and are very fragile. Pieces can break off quite easily.

Ian gets ready to drop into the dive hole.

NATURAL BUOYANCY CONTROL In addition to pumping air into and out of their dry suits, divers can also manage their buoyancy merely by controlling the way they breathe. "Our lungs can hold a surprising amount of air" explains Donna. "If you're underwater and inhale deeply you will increase your buoyancy and will rise. If you make your exhalations longer and more frequent, you'll decrease the volume of air in your lungs and will sink. No arm flapping or swim strokes are needed". " Try it in a swimming pool sometime" suggests Ian "the shallow end" he notes!

Photos courtesy of Karen Cozzetto. May not be used outside this website without her express permission.

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