As a general rule, for anything from snorkeling to scuba diving, you should always choose a watch with a water resistance rating of at least 200 meters. This applies if these are activities you will be regularly subjecting yourself and your watch to. For the occasional swim, a watch resistant to 100 meters will do. The rationale behind the exceptional water resistance we recommend is that, in general, watches tend to perform differently in real-world situations than they do in the laboratories where they receive their certifications. Aside from this, when your life depends on it, as it does in diving, you should always err on the side of caution.

Your watch will become rather useless in the murky depths if you can't read off vital information. Accept nothing less than Superluminova on the markers and hands here, although there are variants that are just as good. As a general rule, Superluminova will stand you in good stead.

For the longest time, professional diving watches were offered in stainless steel but today, the diving watch has been liberated from its steel shackles. You can choose from a wide variety of tough materials, including titanium, and all manner of finishes, from PVD to DLC. Titanium offers many advantages over steel both in hardiness and lightness. Ensure that both crown and caseback are screwed down. Crown (or crowns) and pushers should not be dainty any more than the case should be anorexic. This is one time that size matters.

As an aside here, many high-end professional diver's watches have off-centre crowns and some have helium escape valves. The benefit of off-centre crowns is that they will not interfere with your dive and are reportedly easier to handle. The helium escape valve is present to release helium that may slip past the 'o' rings of your watch at extreme depths and present you with the troublesome possibility that it might explode as you surface. The valve, adjusted manually, allows this helium to escape. There is also an automatic system that does this very same thing.

There's a sea of choice out there for this element but, since you are going up against the elements, look for a strap in rubber, composite or metal. The key thing is that the strap should be expandable (the watch will need to fit outside a wetsuit) and not react adversely to immersion. No leather straps under any circumstances. Look into the possibility of a flip lock clasp that will keep the watch secured to your wrist. There are a variety of guards that prevent clasps from opening, even intentionally.

The bezel must be unidirectional and have luminous markers. The bezel in a diving watch is used to set the maximum time a diver plans to be under so it is vital that it cannot be accidentally pushed or knocked off its setting. Having it move in only one direction means that time meant to be spent under can only be accidentally reduced, not increased.

Before we move on to the watches of the moment, a quick note: Under no circumstances should you take your very fine mechanical watch or watches with you for an adventure in the Jacuzzi or sauna. They may be water resistant but the seals and gaskets that keep the water out don't do so well with extreme heat.