Thursday, June 26, 2008

My variable balast dive

Two posts back I said I would put up a post of a variable balast(belt drop) dive I did back in the late ninties - here it is:

Anecdote: My deepest dive.
On one summer day during a period when I was very fit due to extensive freediving and gym training I decided to do a deep dive to expand my comfort zone. With the echo sounder on we set off from Noordhoek and drove due south past Gasmic[scuba spot] until we reached the 50 m contour. Here the water colour was better than inshore where the visibility was poor. I fastened a 70 m rope to my weightbelt with a small float on one end.
In preparation for the dive I had plugged my mask with kids plastoceine to reduce its volume and thus aid equalization – there were only two small peepholes for navigation. On a previous dive to 47 m I had forced the equalization and suffered considerable discomfort during the last 5 meters of the descent from mask squeeze and an inability to equalize.
My companion, Fanus Gerber, dropped me off in 53 m of water and I took a few minutes to relax and prepare for my dive. After being well relaxed and feeling comfortable I took a deep breath, lifted my left leg and its weight in the non-buoyant air was sufficient to push me below the surface. I gave a kick with each leg and one firm pull with my left hand to accelerate my downward motion. I equalized easily using the Marcante-Odaglia maneuver (pushing the soft palate upwards with my tongue and internally pressurizing my Eustachian tubes without the need to pinch my nose shut). I finned weakly, conserving energy, and gradually descended to about 12 m from where I was negatively buoyant. To conserve energy and air I glided from this point gradually accelerating as my buoyancy reduced due to the increasing pressure. At a depth of around 30 m I pulled my chin in to aid equalization. By now my weightbelt was residing over my chest instead of its normal position on my waist. The pressure reduces ones chest diameter and no discomfort is felt. I glanced at my watch and saw the depth was approaching 40 m. The water was rather dark but this was of little concern to me – I was feeling very comfortable and relaxed. The decent was rapid at this stage and I knew it would be dangerous to crash into the bottom – fortunately the visibility was around 8 m and I saw the bottom with good warning. I tilted a fin to look for the lowest spot and headed for a depression in the reef there I landed on a strange bottom of brittle coral(or perhaps some kind of hard bryozoan) accompanied by another unusual coral – wormlike fingers of a creamy hue. The unusual coral held my attention for a few seconds. I loosened my weight belt, placed it along side and pushed off the bottom. The plugs in the mask had made equalization very easy and I was completely comfortable. I was still negatively buoyant despite having left the weightbelt on the bottom. I paced myself slowly to conserve breath for last part of the ascent where shallow-water blackout is most risky. The upward finning was easy after the descent during which time my muscles were thoroughly replenished with oxygen. On the ascent I was becoming positively buoyant at around 30 m. I looked up and saw the waves and felt surprisingly strong thus far and wished to have been in deeper water. I had requested Fanus to keep his distance in case I swam into the boat*. I popped high out of the surface two minutes and 8 seconds after leaving it. My depth gauge could only measure 50 m and it was maxed-out so I had beaten my previous dive of 47 m and was well pleased as it had felt easy and comfortable.
* I once swam smack into the bottom of a fiberglass boat and was somewhat stunned. If one were to swim into the small skeg(the finlike part that protrudes below the propeller) of an outboard motor there is a chance of knocking oneself out and drowning; so always check the surface as you approach it.

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