An extremely common question I see is whether or not certain gear (mainly regulators) can operate with enriched air / Nitrox. Many manufacturers even claim in their manual that Nitrox is not supported.

It is commonly accepted amongst scuba diving professionals that mixes with less than 40% oxygen are treated as air (with respect to equipment). Enriched air specialties only qualify you to use up to 40%. This means your “air-only” regulator is perfectly fine with any recreational Nitrox mix. No special assemblies or upgrades required, and your tank will not explode on your back underwater.

Interestingly, the flip side of the above “rule” is that any mixes with more than 40% oxygen are treated as pure oxygen.

It’s hard to decide what exposure suit to wear. Here’s a guide to help in the process, which I’ll walk you through using.

To begin, find out the temperature range for the water you’ll be diving in. Let’s pretend I’ll be diving in water that is 72-75 degrees fahrenheit. Next, we’ll modify this range based on several factors:

• Depth – Deeper water tends to be colder, so if this is a deep dive (around 30m / 100 ft), consider subtracting about 5 degrees from your temperature range. In my example, I’ll be diving normal depths around 20m / 60ft, so the range remains 72-75F.
• Duration – What’s your air consumption like? If you tend to dive for over 45 minutes, subtract 5 degrees from the range. My dives will be around 45 minutes, so again, no change.
• Number of dives – Repetitive, multi-day diving needs to be taken into account. If you will be doing this kind of diving, subtract another 5 degrees. Let’s say I’m diving for a week, so my range now becomes 67-70F.
• Female – Women generally get colder than men, so if you’re female, subtract 5 degrees. I’m a man, so no change needed.
• Personal experience – What kind of diving are you used to? Does cold water not bother you much? Depending on your answer, choose a number from near the bottom or top of the range you currently have. I tolerate cold decently, but by no means am I in the Polar Bear Club. Based on personal preference, I’ll use the middle temperature, 70F.

You now have a temperature (in the example, 70F). Plug this into the following table to get a recommended exposure suit. If you find yourself where two ranges meet and aren’t sure what to do, err on the side of too much exposure suit.

Click to enlarge

For our example temperature of 70F, I have the option of a 5mm fullsuit, a 7mm fullsuit, or a 7mm fullsuit with hood. I’ll be diving quite a bit, so I’ll be cautious and dive with a nice, thick 7mm wetsuit. Just for safe measure, I’ll pack a hood in case I get cold later in the week.

Water conducts heat away from your body 20 times faster than air, so the only thing keeping you from freezing after 15 minutes of diving is your wetsuit. Excellent care is a must to keep it insulating well for a long time.

• After a dive

  Most people know this one. After a dive, rinse the wetsuit thoroughly in fresh water. Take a moment and run your hands over it, rubbing away any salt that may try to dry inside. This basic step will do more for your wetsuit than anything else. Don’t forget to do the same after pool dives! Chlorine kills everything—that’s why they use it in pools.

  Also, let the wetsuit dry inside out.

• After a trip

  Every once in a while it’s a good idea to wash your wetsuit down with a shampoo. There are a variety of specialty wetsuit shampoos, but as you know, I like to save money when possible. I find baby shampoo works just fine, and is substantially cheaper. Throw in a little baking soda as well to really neutralize any odors (read: pee smell).

• Storage

  You have two options for storage. Ideally, get a wetsuit hanger or a thick plastic hanger for storing your wetsuit in a closet. Make sure the wetsuit hangs in a form-fitting fashion, to prevent awkward creases. Don’t use a metal hanger.

  If hanging the wetsuit is not an option, you can fold it for storage. Be careful that you don’t put any creases in the wetsuit, and minimize the amount of folding needed. For instance, try to fold it once longways (putting the arms and legs on top of each other), and then one more fold across the waist area.

  Try not to squish it under anything. Permanent creases deteriorate the insulation quality of wetsuits.

• Repairs

  It’s a good idea to check for little holes or tears, while they are easier to fix. Most small tears can be repaired with neoprene cement. Loose patches and seams may have to be repaired with bonding cement.

  If the hole is too large to bond back together, a neoprene patch is probably required.

Follow these basic guidelines so your wetsuit keeps you warm for years to come. And remember, an old wetsuit doesn’t have to go in the garbage. Use them for activities where a wetsuit is needed but either the water is really warm (you don’t need perfect insulation) or you don’t want to use your new wetsuit. Pool dives are a great example.

Last weekend we were in a local dive shop killing some time. We saw some fabric paint for sale that was meant for writing your name on gear, or drawing pretty pictures, who knows. How much? 8 bucks.

Looking closer, we saw that the label, which said something like, “Scuba Dive Gear Paint”, was actually affixed on top of another manufacturer’s label. My girlfriend, Maritza, pointed out the manufacturer, telling me they sold that brand in Michael’s, the arts and crafts store.

Later that day we happened to pass by a Michael’s, so we stopped in. Sure enough, we saw the exact same bottles of paint. Cost? One dollar.

If you’re looking to mark up your gear, don’t buy “specialized” paint from a dive shop. Go to an arts & crafts store for the same stuff. Here is the kind of fabric paint we bought.

One fish I really enjoy spotting is the spotted drum. It’s not uncommon to find one, but it’s infrequently enough where they’re not boring.

Physical description

Spotted drum are about 6-9 inches in length (about 20-something centimeters). If you see one, you will know it. It is an easily recognized fish that is white with broad black stripes in varying directions. The dorsal fin and tail are usually adorned with white spots. If that isn’t distinguishable enough, they have a long, white and black “feather” connected on top of their body, between the head and dorsal fin.

Geography and Habitat

Spotted drum are found on coral reefs in the Caribbean, Gulf of Mexico, Florida and the Bahamas. They can be found at all recreational depths. They swim alone, usually under cover of a ledge, coral, or the opening of small caves. For this reason, you will need to get low to find them.

Spotted drum are nocturnal, so it’s possible to find them out feeding during a night dive.

Further reading

Fishbase.org

Split fins are a relatively recent invention, developed in the late 90’s. They are easily recognizable as fins that are, well, split down the middle. Before we get into them, let’s talk about basic fin design.

The purpose of fins is to convert the up-and-down motion of a kick into forward thrust through the water. The more efficiently it does this, the less energy it requires for you to move, since a higher percentage of kicking energy is converted into thrust. This efficiency is generally what makes one fin considered “better” than another.

Most full fin designs have some sort of ribs on the edges and possibly in the middle, creating channels along the fin. This directs water along the fin, ensuring that most of it gets pushed backwards, in turn pushing you forward. The ribs prevent water from “spilling over” the edges of the fin.

This is straight-forward, but things start getting fancy with split fins. Split fins are in principle similar to a propeller, which uses hydrodynamic concepts to turn rotational motion into forward motion (i.e., the blades spin and the plane / boat moves). As you kick, the fins angle inward, forcing water down a narrow channel. This creates a pressure differential that, along with the water running down the channel, helps propel you forward. (Note to physics geeks: see Bernoulli’s Principle)

Ok, sure, but what does it mean? Basically, that you get more motion for the same amount of kick. Split fins are more efficient and thus, “better” by some definition.

It’s not all good, though. This description only applies for the usual flutter-style kick. If you are a frog kicker, split fins will actually be less efficient than ordinary full fins. For this reason you won’t see split fins on a lot of wreck or cave divers.

Split fins are also expensive, costing 2-3 more than regular fins. It’s up to you, whether the extra cost is worth the increased kicking efficiency. Besides, fins are probably not the most expensive piece of scuba equipment you’ll buy (even split fins), so when you factor in their lifespan, the extra cost becomes less significant.

I use these split fins from Apollo. Although I haven’t had much experience with other fins, I really enjoy them.

In the end it comes down to the importance you place on kicking ease and your budget. However, next time you shop for fins, at least check them out and see if they work for you.

Dive trips are exciting, but can be a real chore when it comes time to pack for the flight. There’s the advantage of having all your own equipment and not using questionable rentals versus the task of getting it all to your destination.

Dividing equipment between carry-on and checked luggage can ease the burden slightly. Then the problem becomes, “What equipment should I check?” Here are four considerations to help with this decision:

• Legality

  If you’re not allowed to have it on a plane, then the decision has been made for you; so don’t even bother with that dive knife. I’ve heard mixed results from carrying pony bottles, with most saying they are fine. Check with the TSA’s (if flying from the US) set of ever-changing rules for up-to-date information.

• Cost

  How expensive is the particular item? Don’t expect the airlines to reimburse you for broken goods, just ask this guy. If it’s expensive, you may want to consider carrying it with you.

• Breakability

  Likewise, if something is likely to be broken when tossed (even inside a case), it also may be better off with you. There is a variety of luggage specifically designed for protecting dive gear, so you may want to give that a try. Keep in mind, however, that security may go through your bag and not put all the pieces back in exactly the manner that guarantees their safety.

• Importance

  How easily can you go without something? More so than just breaking something, luggage can get lost. If a checked item doesn’t show up until the end of the week, will it significantly affect your diving? For this reason, most people will forgo their own weights on trips.

• Space

  If it won’t fit in an overhead space, then the choice has been made for you; either check it or leave it at home.

If you still have no idea what to do, then here’s a starting point:

Carry-on: regulator, mask (especially if prescription), camera equipment.

Check: BCD, fins, snorkel, wetsuit, knife.

Use the above criteria to tweak these lists until you are satisfied.

Previous posts have discussed the importance of proper buoyancy. Here I describe how to do a simple weight check in the water.

1. Initial weight

   If you don’t know where to begin, take about 10% of your body weight. If diving in tropical waters with a thin wetsuit, subtract 4-6 pounds; if diving in cold water with lots of exposure protection, add 4-6. This will give you a starting weight to tweak.

2. Enter the water

   Begin at the water surface with full diving equipment and an inflated BCD.

3. Hold a normal breath and deflate your BCD

   At this point you should find out if you are properly weighted. If you sink, you are overweighted, if you bob out of the water, you are underweighted. An ideal weight will keep you approximately eye-level.

4. Repeat

   Based on feedback from the previous step, adjust your weight accordingly and repeat until you float at eye-level.

5. Compensate for your cylinder

   If you are doing this check with a full cylinder, you should add about 4 pounds to compensate for the end-of-dive when the cylinder will be more buoyant. Trust me, it won’t be fun kicking to stay underwater during the safety stop.

That’s it! Once you have a proper weight, note it in your dive log to save time in similar diving environments with the same exposure protection.