In Dauin we have a dive site called pyramids, with a number of nicely overgrown pyramidal artificial reef structures. A tad below the pyramids, at about 28 to 30 meters, grows a large black coral. As so often, things are not what they seem: the black coral is in fact snow-white when alive underwater, and only black when in a sad dried state (often as a part of jewellery – don’t buy that kind!). This wonderful white black coral is the home to a number of very interesting animals:
A juvenile file fish:
The always curious dwarf hawkfish:
And, most interestingly the rare, weird and unusual saw blade shrimp (Tozeuma armatum)! A shrimp which looks like a branch of the white black coral! I would think that even other shrimp are amazed by this shrimp!
So, you’d want to look at the amazing saw blade shrimp, you have to dive to 30 meters. And there you will not be able to stay for too long: Tick, tick… your no decompression time (NDT) starts counting down. When you arrive at 30 meters, depending on your dive computer you will have about 18 minutes left before you need to ascend. The PADI dive tables give you 20 minutes of bottom time at 30 meters, and you will need at least 2 minutes to swim down. Then, it takes you 6 minutes to find the saw blade shrimp …. 12 minutes left …. You admire the animal, and possibly take a few pictures, …. your computer shows you 3 minutes of NDT left, and as a careful diver you start your ascent before your NDT reaches zero. It was a nice dive, but you are craving for more shrimp-time, and really regret having to end your dive.
Why did you have to end the dive? As certified divers we know that it’s the atmospheric nitrogen which we take up into our tissues at high ambient pressures during a dive. There, it forms harmful bubbles upon ascent when we come up after a too lengthy stay at depth. Our dive tables or computers tell us for how long we can safely stay at one depth. How can we delay this process? We can breathe in less nitrogen! This can be achieved by replacing some of the nitrogen in our breathing gas (normal air) with oxygen. The resulting gas is called enriched air, or nitrox. Some of extra oxygen is metabolized, and this gas will not form dangerous bubbles in your body. The reduced amount of nitrogen in nitrox means that you will take up less of this gas during your dive, and your no decompression time will be extended. A very common nitrox mix is nitrox-32, with 32% of oxygen, and hence only 68% nitrogen. The reduced amount of nitrogen will give you, according to the PADI tables, 30 minutes of dive time at 30 meters! Yeah! More quality time with the amazing saw blade shrimp! Your dive computer might give you slightly different no decompression times, but the increase in allowed time at depth will be similar.
Interestingly the concentration of oxygen in the atmosphere was not always the same in the history of the Earth. Back in the Carboniferous geological epoch, 300 million years ago, it was up at 32% (it’s 21% right now)! Ah, the Carboniferous, the good old times! Free nitrox for everyone back then! At Salaya, the first quarter of 2018 is almost as awesome as the Carboniferous. For every fun dive we are giving you free nitrox (we always do that) and the course you need to qualify for diving with nitrox is discounted.
PADI is promoting the Enriched Air Diver Specialty course in the first quarter of 2018 as the “Specialty of the Quarter”. That means you’ll get 10% off the regular course price at Salaya, and 15% off if you take both this course as well as the other Specialty of the Quarter, Deep Diver (more about that next week). Come join us on some nitrox dives!