IWC Portofino Automatic Red Gold Diamond Bezel (IW3565-15)

A symbolic depth of 300 metres, or more correctly a water resistance tested to 30 bars of pressure, seems to be a widespread norm for diver's watches. Yet the ISO 6425 standard, by which such diver's watches are homologated, requires only that the watch be water resistant to "at least 100 metres".

Against this benchmark, the watches that we are looking at here are overengineered, in some cases to the extreme. While a professional diver may indeed find himself working at a depth of 300 metres, this represents the limits of mankind's resistance. The deepest recorded dive, by divers of the Comex S.A. industrial deep-sea diving company in 1988, was 534 metres…

500 metres
Despite its water resistance to 500 metres, the Carl F. Bucherer Patravi ScubaTec still resembles a "normal" diver's watch and is even proposed in versions with a case in precious 18-carat rose gold. Its rubber strap (or stainless-steel bracelet with diving lock) and rotating bezel with clear indications single it out as a diver's timepiece, while its 13.45mm thick case, with a 4mm thick sapphire crystal, helps to ensure the extreme water resistance. A helium valve allows the gas to escape during saturation diving. Chronometer-level timekeeping is provided by the CFB 1950.1 self-winding movement, which has a 38-hour power reserve.

The Scafodat 500 by Eberhard & Co. is, as the name suggests, also water resistant to a depth of 500 metres. Its oversize triangular hour markers at the four quarters give it the appearance of a compass and a separate crown at 4 o'clock - also oversize - operates a rotating flange (available with white or red numerals) underneath the 3mm thick sapphire crystal to record dive times. The Scafodat 500 relies on the ETA 2824-2 self-winding calibre for its timekeeping functions and has a stainless-steel bracelet with a patented system for lengthening and a patented folding clasp, or a rubber strap as shown below. An automatic helium escape valve is secreted in the case middle.

1000 metres
Updated in 2012, the latest Sea Hawk models from Girard-Perregaux turn the familiar aesthetic codes of a diver's watch on their head. The crown is shifted to 4 o'clock and enclosed within a protrusion on the case for extra protection; the power reserve indicator is found at 6 o'clock, while the small seconds and date are in the unusual positions of 10 o'clock and 2 o'clock respectively on the "honeycomb" dial.

The 44mm diameter case of the Sea Hawk is 17.1mm thick, guaranteeing water resistance to a depth of 1000 metres. A helium escape valve means that it, too, is suitable used for deep-water saturation diving. Girard-Perregaux's in-house GP03300 self-winding calibre with a 46-hour power reserve drives the watch at 28,800 vibrations per hour.

2000 metres
IWC has built a considerable safety net into its 46mm diameter Aquatimer Automatic 2000, which has a case 20.5mm thick that is water resistant to 200 bar - far beyond anything that a human being can endure. Bearing a resemblance to the brand's Porsche Design for the Ocean 2000 model, the Aquatimer Automatic 2000 is slightly larger yet, thanks to its titanium case, easily wearable. It is powered by the IWC in-house 80110 calibre, which has a 44-hour power reserve, and is fitted with IWC's patented bracelet quick-change system, which allows the rubber strap to be swapped easily for a metal bracelet.

If you're planning to go diving this summer, or perhaps bungee jumping during your holidays… or even if you simply want the feel of a highly resistant timepiece on your wrist, you have plenty of choice.