While you're down surveying the coral at 120 metres, you should be able to glance at your Patek Philippe Nautilus to check if it's time for cocktails back at the hotel.
How do they do that?
How is a delicate, intricate machine like the watch waterproofed so successfully it keeps time perfectly at 13 atmospheres of pressure?
To give that some context, the air in your car tires has a pressure of 2 bars, which is 2 atmospheres.
And it's salt water, which is bad news for metal.
All this has to be achieved in a form that is elegant enough to look lovely when you surface for your mai tai.
Many consider the Nautilus to be the most beautiful watch ever made. Image Patek Philippe.
Let's take a look inside a Nautilus, surely the world's most desirable piece of diving equipment, and see how it works.
Why tell the time underwater?
Luxury watches come in two broad categories:
Dress watches and professional watches.
The Nautilus's appeal rests on how it straddles these categories.
It is a called a sports watch, and it takes on some features of the divers' watch.
They're probably the best-known professional watches, though racing driver's watches like the Rolex Daytona run them close.
Professional watches deliver the special functions that a diver, pilot, athlete, racing driver, or even nuclear physicist (the magnetic resistant Rolex Milgauss) needs in their work.
Divers need to know the time.
Accurately.
At great depths. Some watches can go down to 3,000 metres and beyond.
They also need an elapsed time mechanism of some sort, so a diver knows they're not going to run out of oxygen or exceed the safe time at depth.
This is usually a one-direction rotating bezel: the frame on the front of the watch face, that allows the user to set a fixed time marker independent of the ever moving hands.
The Nautilus: for swimmers who are smart
A Nautilus is nearly a professional watch.
It doesn't meet the ISO 6425 standard for a diving watch.
And when it was first released in 1976 it was hailed as an innovative new style of watch.
It has some professional watch functions.
Without adopting their more functional aesthetic.
It's often called a sports watch.
So Lionel Messi looks fabulous flashing his 18-karat white-gold Nautilus Perpetual Calendar Ref. 5740/1G at press conferences.
And, if he wants to jump in the pool afterwards his watch will be fine.
How the Patek Philippe Nautilus keeps water out
The first recognised divers' watch was a Rolex Oyster. It was released in 1927.
Rolex used cross-channel swimmer Mercedes Gleitze to help sell their new innovation in 1927.
That was the name of the case style, for which Rolex bought the patent.
The case is key.
Divers watches must keep out water with a sealed, water-and-air tight case.
The Patek Philippe Nautilus does this with:
Steel.
Steel was a selling point - something different, new, and modern.
Steel is now a very fashionable choice for watches that won't go anywhere near the water.
But it's chosen over more traditionally desirable precious metals for underwater use because it's strong enough to survive high pressures and it resists salt water corrosion.
Gaskets
Gaskets are seals - flexible layers that form around and between inflexible surfaces (like steel) to form an impenetrable whole.
Patek Philippe use rubber gaskets to complete seals around its case.
To keep water out, these gaskets are compressed when the case back and crown are screwed tightly in place.
Points of vulnerability
Water loves joins and joints. A watch could easily be made waterproof if it had no moving parts and no access requirements.
But, mechanical watches do need to be opened from time to time.
And their controls - winders and pushers - need to move in relation to the case, opening another point of vulnerability.
The original Nautiluses had a monoblock case. As the name suggests, this eliminated joints by encasing the movement in a single block of metal.
The movement was put in from the "top" of the watch.
The crystal through which the dial is viewed still had to be attached in place via a screw-down crown but the case back was solid.
However, more recent iterations of the watch have reverted to a 3-part case (crown, back, and body), which is easier to make and maintain.
Weakness
We cannot see through steel.
So, watches designed to survive underwater need to hold a transparent surface over the dial.
The Patek Philippe Nautilus uses scratch-resistant sapphire crystal glass.
Some references give an inside view of the mechanical genius inside your Patek Philippe Nautilus.
A score of 9 on the Mohs scale means it won't scratch if you do rub against a reef.
Anti-reflective coatings on both sides of the crystal mean you don't lose any visibility while you're under water.
The bezel on the Nautilus is a much-loved design element.
Clever marketing helped to sell the Nautilus on its launch.
The look was supposed to mimic a luxury liner porthole.
And, it delivers function. The bezel, with four screws, holds the crystal and pushes it super tight against the frame and its sealing gasket.
The same mechanisms hold the rear crystal in place to enable the owner to see the movement via the rear of the case.
Working parts
While we've explained that a Patek Philippe Nautilus isn't a fully functioning divers' watch, it's still a very high-powered piece of mechanical genius.
Those models that have a chronograph (stop watch) need controls to start and stop the timer.
These pushers can be screwed into their tubes, compressing gaskets and making a watertight seal.
They also make it impossible to stop or start a stop watch once you're underway. This is a great safety measure when you need to know exactly how long you've been underwater.
Beautiful, functional, desirable
The Patek Philippe Nautilus is a wonderful combination of form and function.
The fact that production of the line was halted in 2021 has only made them more desirable.
There was a reported decade-long waiting list for the classic 5711, despite its closing $30,000 price tag, at that point.
The watch had been in production since 2006. That's quite a while for what is essentially a fashion item.
Don't worry, there's a new version, the 6711, and the Aquanaut line is cut from very similar cloth.
Just as good? Will the Aquanaut become a cult hit too?
And, there may be complex commercial reasons - in part related to the Nautilus's extraordinary secondary market performance - for pulling the plug on the legendary reference.
Nautiluses are commonly on sale for around £100,000. A Chanel-branded special edition was auctioned for $6,5 million in 2021. It may well be the most desirable collector's watch there is.
Finding a good, pre-owned Patek Philippe Nautilus
Paul Fraser Collectibles are specialists in pre-owned watches.
We buy. And we sell.
And if you'd like to buy or sell we can help you find the right watch. Or get the best price.
We have wonderful collector and industry contacts.
To give us a try - and perhaps find your own Patek Philippe Nautilus - simply drop an email to info@paulfrasercollectibles.com or call on +44 (0)1534 639 998.
And for watches, now is really the right time to call.
