Scuba diving is fun. It's exhilarating. It's amazing. And it's very expensive. Even for the casual vacationer out to try it for the first time, it can suck the traveller's cheques right out of those ridiculous Speedos. Casual tries inevitably lead to serious diving, and no real diver would ever go without their own equipment. So, in order to be properly equipped, shell out your hard-won dough on the following essential items:

Dive Suit

Even in tropical waters, your body will lose heat. This is because water transfers heat faster than air. That obnoxious Speedo that kept you warm and toasty above won't be enough below, especially as you get deeper. There are several options, and your choice will depend largely on the temperature of the water.

Dive Skins:Lycra, form-fitting suits that offer minimal thermal protection. They are useful in tropical climates, especially as they offer a measure of skin protection without holding in excess heat. In colder climates, many divers choose to wear a dive skin under their wetsuits, which makes the wetsuit easier to take on and off.

Neoprene Wetsuits: Composed of neoprene, which is a porous, spongy, rubbery-type fabric. The theory is that it will allow a small bit of water in against your skin, and hold it there. Your body will heat the water, and it will act as an insulating layer between you and the suit, and thus the rest of the ocean. In practice, however, it doesn't quite work out. Your body's motion will tend to squeeze out the old water, and as the pressure is released, fresh, cold water rushes in to take its place. Still, it does provide some insulating qualities in its own right. Buy one that fits snugly against you to minimise heat loss. Wetsuits can be purchased in a variety of thicknesses, measured in millimetres, for a variety of environments. There are also varying styles, from the 'shortie¹' to the two or three pieced versions that come equipped with a hood. Another benefit of wearing one is that the covered areas are protected to some degree from scratches from rocks, corals, and other hazards.

Dry Suits: This is the sort of thing an astronaut would wear if he went underwater. It is a completely sealed suit that permits no water to get into the diver. Generally not used recreationally, since water cold enough to merit this generally attracts few tourists.

Fins

Nothing much too say here, they're fins. They allow you to propel yourself. Don't buy the full-footed ones, since they'll come off easily. You'll also need to wear a pair of neoprene boots, to prevent the straps from chafing your feet. It is recommend you get a set with a buckle on the straps, because they make donning and doffing incredibly easy. It doesn't seem like such a big deal until you try exiting that first beach dive, and find yourself struggling to loosen the straps before the waves dump you on the shore. Otherwise, just make sure you get a set with a stiffness level that you're comfortable with. Fins that are too floppy will force you to work to hard, as will ones that are too stiff. Buy these at a dive site with a pool in the back, and insist on taking them for a test dip.

Mask

You can't see without one, or at least without squinting, and some major discomfort. So to avoid a permanently scrunched-up squinty expression you'll need a mask. Get one with as wide a viewing angle as possible, and test it for fit in the shop. This is accomplished by sticking it on your face, and inhaling through the nose. If it sticks to your face, and you get little or no air leaking around the edges, you've found a winner. No mask will keep all water out, but a good fit ensures you'll draw a minimum of water. You might want to consider sparing the expense for one with an exit valve in the bottom of the nose, which makes it easier to clear out any leakage.

Snorkel

Why does a diver need a snorkel? Simple. The air in your tank is a limited resource. When diving from the shore, you'll usually have to swim out a couple hundred meters to get to the good parts. If you can make that trip on the surface, breathing through the snorkel, you'll be able to extend the length of the dive. Even if you're diving from a boat, it's still a necessity, for emergency purposes. The current may take you far from the boat, or you may injure yourself, and be unable to reach it. The snorkel means you'll be able to bob along on the surface indefinitely until help arrives.

Snorkels help keep the water out of your lungs, and are considered 'a good thing'. When a wave washes over you, it can wash over the top of the snorkel, flooding it. A purge valve at the low point of the J, similar to that found on some masks, makes purging water intake easy. Streamlined intakes minimise the flooding, and another valve near the top can divert most of it harmlessly away from you.

Tank

This one is pretty obvious. Just make sure it is in good condition. This is the one piece of mandatory gear that it may be a good idea to rent, as long as you use a reputable dive shop. The shop will perform regular maintenance way more often than you would, so you'll get a quality, if slightly scarred and unattractive, piece of equipment. Inspect it yourself before you take it with you, and observe them testing the pressure for a proper fill.

If, however, you have unlimited access to outstanding diving, and have decided to do this every weekend, you'd probably best buy your own. The most popular type is the 'Aluminium 80', imaginatively named because it is constructed of aluminium, and holds up to 80lbs of compressed air. Steel ones are available as well, but their weight isn't worth the extra few pounds of air capacity. Small people can also purchase tanks smaller than the 80s, but will do so at a severe cost of bottom time. An accessory for the tank is a nylon, webbed netting sleeve that can make life simpler. The netting will help keep it from slipping out of its berth, and the bottom of the sleeve ends in a plastic butt that helps keep the tank upright.

A few rules about tanks:

• Always inspect the rubber gasket at the exhaust valve before using.
• Never leave a tank upright and unattended. It can fall and explode, or become a missile.
• Keep up with the maintenance. Take it to the shop once a year. They'll perform a VIP test, which involves inspecting the valves for corrosion, inspecting the interior of the tank for corrosion, and pressure testing for leaks.
• Always keep at least 500psi in the tank. If the tank runs dry, you'll have to get it re-VIPed.

Regulator

This engineering marvel provides your air, and comes in two parts:

First stage: This is the part that attaches to the tank. It snugs up against the rubber gasket, so a missing or frayed gasket will allow salt water into your tank, causing tank corrosion, and respiratory problems to you. The first stage distributes the air to the different components that need it, through high and low pressure ports. Spare no expense on this item, because your life depends on it. You'll want to make sure you have enough output ports for your various accessories. You'll also need to have it serviced once a year.

Second stage: This is the part you put into your mouth. It attaches to the first stage via a low pressure port and rubber hose. It basically consists of a demand valve, with a rubber diaphragm activating it. As you inhale, the negative pressure you exert pulls the diaphragm toward you, opening the valve and allowing the air to flow to you. Exhaling then presses the valve closed. There are many different models, and tons of factors to consider which sort of second stage you want. The first consideration should always be comfort. If you're working too hard to breathe, your dive will be much less pleasant. Likewise if you're being force-fed. This is adjustable, but you may want to consider one with bulky knobs that can be adjusted at once over one that requires an Allen-wrench. Size and streamlining are also considerations when making a choice. The second stage is another complicated piece that your life depends on, so have it serviced as well.

Octopus

Octopus is a fancy name given to a spare second stage regulator. It also occupies a low pressure outlet on the first stage. You'll need to have one in case your primary second stage fails, or in case your partner's air fails entirely. Since this one will only be used in emergencies, it isn't necessary to purchase one with lots of fancy features. Keep this one simple. Look for something that is slim, so it'll produce less drag as you swim. Octopi are always painted bright colours, usually neon yellow, to make them easy to locate.

Console

This is where your vital dials and meters can be found. It connects to a high pressure port on the first stage, and provides measurements of tank pressure, current depth, deepest depth reached, and water temperature. It's a good idea to mount a compass in the console, as well.

An alternative to the console is a dive computer. It plugs in the same way, and monitors all the things the console does, but in an easily readable digital format. The computer is also programmed with the dive tables, and it will monitor your dive and update its calculations regularly, and make recommendations to the diver as to when it is time to begin ascent, and whether a safety stop is necessary. These don't come cheap.

Buoyancy Compensator (BC)

This is the unfashionable nylon vest worn by divers over the wetsuit. The back contains the straps for securing the tank, and hooks and rings allow the rest of your gear to be secured for convenience and streamlining. An air bladder runs throughout the vest, which, when inflated, provide positive buoyancy. The inflation hose ends in a valve that can be operated manually, and connected to a low pressure air port on the tank for auto-inflation. Another button allows air to be released. Purge valves prevent the bladder from bursting from accidental over-inflation.

Buoyancy control is the most sophisticated skill a diver must learn. Too much buoyancy means the you must work to stay at depth, and too little means you will be dragging along the coral and killing the environment, or, worse yet, cause you to drop like a stone. As you descend, the air in your BC will contract, causing you to lose buoyancy and drop faster. Conversely, air in your BC expands as you ascend, causing you to gain buoyancy and rise faster. Since slow, controlled ascents and descents are required for safety's sake, it is vital that the diver learn to anticipate and react. During the dive, perfect neutral buoyancy will allow the diver to relax more, and enjoy the scenery.

Features to look for in a good suit are comfort, fit, and function. Lots of D-rings for attaching accessories are a bonus, as are large, easily accessible pockets. Try out the tank strap system for snugness and ease of use. Integrated weights are an outstanding design feature for comfort.

Weights

The human body floats in seawater. The air tank provides a measure of negative buoyancy, but this is counterbalanced by the positive effects of the buoyancy compensator and any neoprene products worn (wetsuit, gloves, boots). In order for you to get to the bottom, you're going to need some lead. Weights are worn in one of three ways:

Cast weights: Lead blocks cast into a shape that will allow a nylon belt to be threaded through them, which is worn around the waist. They're extremely uncomfortable, and will generally leave impressions on your hips. They're also notorious for shifting around during the dive, which leads to an extremely annoying starboard list.

Plastic coated weights: Same as the cast ones, except that they've been coated in plastic. They slide around less, and are slightly curved to fit better against your body. They'll still leave impressions, but you won't be as sore.

Lead shot: Nylon bean bags filled with tiny lead spheres. They mould themselves to the body, and so produce minimal discomfort. They can be worn in a specially designed belt around the waist, with isolated pouches that keep them from sliding around in the belt. Or, they can be stuffed into pouches designed into your BC, if you purchased one with integrated weight capability.

Regardless of which option you choose, carrying the right amount of weight is very important. Weights are sold in two, three, and five pound sizes, and you'll need to mix and match to get to your correct amount. In order to get there, however, you'll need to experiment a bit. Some people float better than others, and your choices in dive gear will further affect your buoyancy. The optimal weight is that you require to achieve neutral buoyancy at a depth of five meters, with all of your dive gear on, your BC completely empty of air, and a tank containing 500psi of pressure. For those who lack the time or resources required to experiment, just take on as much weight as you require to achieve neutral buoyancy at five meters with a full tank, then add a couple more pounds. When you've determined your required weight, you'll then want to ensure you distribute that weight around your middle in such a way that you can avoid the aforementioned starboard list. Split the weight between your sides, and place any that doesn't divide well at your spine.

All weight systems are designed to be easy to ditch, in case of emergency. For instance, if your buddy lapses into a narcoleptic doze, dumping his weights will send him or her to the surface. Make sure you're familiar with how to ditch your own weights, and share this information with your partner, who should do likewise for you, before you enter the water.

Knife

Universal cutting and prying tool. It's a good idea to carry one on your person if you get tangled up in any sort of lines or nets. You'll also want it handy if you get bitten by an eel, since it's the only thing that'll separate you from its head. They also make good prying tools, for digging up shiny things to show your friends. Many knives come with a blunted tip for this purpose.

You'll want to wear it on the inside of your lower leg, for two reasons. It'll be easy to access there, and it'll be out of the way if you're forced to ditch your weights. If they manage to tangle in your knife sheath, you're in trouble.² Some divers, motivated either through paranoia, or simply the joy of surrounding themselves with deadly weapons, also choose to wear a smaller version that clips to the BC.

Regardless of your choice in size and style, buy stainless steel, which isn't really stainless, since it will rust, but will do so much less than any other material. Make sure the blade will come free of the handle. You'll need to disassemble it after each dive and clean it, or else it will deteriorate inside the handle and eventually fall apart.

Dive Flag and Float

Underwater is dangerous. Above water, there are creatures even more dangerous. Odd bipedal creatures, who operate noisy machines that propel themselves by violent means. They aren't much danger to the adequately submerged diver, but you have to surface sometime. By international maritime law, all divers are required, for their own safety, to fly the 'Bravo'³ flag. It is a red flag with a white diagonal slash running across it. When diving from a boat, the flag can simply be flown from a jackstaff on the vessel. When diving from shore, however, you'll need to tow your own. You'll need a flag, a float, some anchor line, and something to anchor it with (a spare cast or coated weight works wonderfully for this). Then you'll have to tow it out to the general area where you wish to dive. Skip the flag, and you can expect a weighty fine from the local authorities.

Watch

It is vital that you watch your bottom time⁴ to avoid the risk of decompression sickness or air embolism. Setting the alarm is a good prevention method. The stores will try to tell you that you need a special watch, but generally, that cheap Timex that says it's only 'water resistant'⁵ to 100 metres will stay dry just fine.

Extra Safety

Pony Bottle

Also known as a 'spare air,' this is an excellent tool to have along in case of air loss. Rather than catching your buddy's attention, you can simply pull out this small container of compressed air. A demand valve and mouthpiece is mounted on the top. It only holds enough air to last you a few minutes, but this will be plenty of time to make a controlled ascent.

Strobe Light or Coloured Light

Having one of these along on a night dive is especially useful. When diving from shore, these beacons will help you find your exit point, and provide a reference point for further navigation. When spear hunting, it's a good idea to put a light in the catch bag as well, so you'll be able to range out from it to find game, rather than dragging it alongside. Putting a beacon on your dive float is also an excellent idea, to make it easier for people to see, and easier for you to find when it's time to go in.

First Aid Kit

It's quite easy to suffer the odd cut or scrape while diving. The ocean contains far more contaminants than the air does, so, by the time you reach the surface, your wound is infected. Some isopropyl alcohol, some antibiotic cream, and a few bandages later, you'll be just fine.