While working on a reference article on pressure-depth relationships, I was reminded of divers I had a few years ago. This couple has a creative way of finishing a dive. After maintaining a reasonably well-controlled safety stop, they both reached for their inflator hoses and pffffffffttt held down their inflate buttons and shot to the surface from 15 feet. When I chatted with them about this dangerous habit, they told me that their open water instructor taught them to ascend this way.

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A client came into a friend's dive shop and announced "I want to go dive Cozumel!" This gentleman was not a certified diver. When my friend explained that his dive shop only takes certified divers to Cozumel, the client decided to take the Open Water Diver Course. While a certification course may have been the correct decision for this client, it brings up the question: why are people getting certified? If it is just to say they went diving on a famous reef or to check out some pretty tropical fish once every few years on vacation, certification may not be not the correct decision.

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"Make sure you turn on your oxygen," a scuba diver reminded his son. I understood that the diver simply wanted to make sure that his son had opened his tank valve before gearing up, but hearing someone refer to a recreational scuba tank as containing pure oxygen makes me do a double take. Perhaps the father merely lacked precision of language, but it seemed to me he lacked something more fundamental: understanding. Diving with pure oxygen can kill a diver even at shallow depths.

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A certain kind of diver makes guides groan. This diver assembles his gear, and then reaches for his dive bag and breaks out the accessories. I watch in disbelief as he slides a mesh tank protector over the rental tank, and then proceeds to clip on to his buoyancy compensator large slates, a magnetic etch-a-sketch, dive tables, blinking tank strobe lights, a tank banger, low pressure hose noise maker, a shaker, a camera, a fish ID slate, a flash light, fancy octopus holder, a surface marker buoy without a reel to deploy it, mesh collecting bags (for trash?), and various types of extra clips and hose retractors "just in case". In the dive industry we call this kind of diver a "Christmas tree diver" (CTD) because he has so many doodads hanging off of him that he looks like a well-ornamented Christmas tree.

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The temperature at the water's surface is about 78º F --  a hot day back home for most of my students. When it is time to don their wetsuits, my students sometimes groan and complain about squeezing into the tight neoprene. Many of my beginning divers even refuse to use a wetsuit! With rare exceptions,  these divers come up shivering. Before heading to a tropical dive paradise for your summer vacation, consider the following reasons that you may need a wetsuit even in warm water.

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If I stand on a dive boat and squint out to sea, I can see the gentle curve of the horizon. The ocean stretches left to right, filling my entire field of vision. Sometimes I forget how enormous the ocean is. The amount of water and the diversity and quantity of life it holds are impossible to comprehend. As I look over the ocean, I am humbled by power and vastness of the water. Divers immerse themselves in an element much stronger than a human being. We must remember to approach diving with a sense of respect and humility, for we are guests in a foreign environment.

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How much should you tip your dive guide and crew? It is so confusing. The answer varies according to geographical location, dive shop, and the staff dynamics. Tipping dive guides and the boat crew is a standard practice. Unfortunately, tips can also cause jealousy between dive shop personnel . In the worst scenario, improper tipping protocol can lead to your tip being distributed in ways other than you wished. The question becomes not only how much to tip, but who to tip, and how.

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Do I get tired of diving the same reefs over and over? If I were just looking at a coral reef, I might be a little bit bored. Reefs are more-or-less the same on every dive, but the marine life I find on the reefs is not. When I am diving, I enjoy watching the different behaviors of fish, and love searching for tiny creatures like the Banded Clinging Crab (in the photo) that are hard to find. Nearly every time I go underwater, I dive with different conditions, aquatic life, and dive buddies. Every dive is an adventure, and I look forward to every dive with anticipation. As I roll off the boat, I think: What will I find down there this time?

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I just purchased Nuvair 02 Quickstick oxygen analyzer. (Oxygen analyzers are used to analyze the percentage of oxygen in a tank containing Enriched Air Nitrox.) When I received the analyzer, I read the instructions (not a typical move for me). Low and behold, I learned something new! Some analyzers need to be calibrated differently depending upon the temperature and humidity of the surrounding air.  If  I am a nitrox instructor and was never aware of this,  I imagine that most recreational divers aren't aware of it either.

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Electronic pressure transmitters are one of my most hated pieces of dive gear. These small transmitters attach to the regulator first stage and electronically beam information regarding tank pressure to a diver's wrist-mounted computer. This eliminates the need for a diver to reach all the way down to his submersible pressure gauge, laboriously tilt the gauge window towards his face, and advert his eyes for a whole split second to read the gauge. Electronic transmitters are a waste of money. A diver who needs an electronic transmitter because he has difficulty accessing his submersible pressure gauge  probably shouldn't be diving in the first place.

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