Dive timing
Aquastar Deepstar.
The 1962 multiple-dive no-decompression chronograph. Its bezel was calibrated to the French Marine Nationale decompression tables of the era. The same scale geometry sits on every Aquastar Deepstar made today.
What makes a tool watch
Single purpose, built into the case.
A tool watch is engineered for a job, not for an audience. Its case is shaped by the conditions it has to survive. Its bezel, its dial, and its complication are answers to one operational question: what does the wearer need to read at a glance, under stress, while doing the work?
Aquastar founder Frédéric Robert filed eleven patents between 1957 and 1977 to answer that question, one watch at a time. The 1964 no-decompression bezel. The 1965 dual-gasket crown that made a serviceable 500-meter case possible. The 1966 improved bathymeter for the Cousteau-Comex saturation programmes. Each invention was a tool for a specific problem a diver, sailor, or pilot put in front of the workshop.
Read more about the patent that defined the modern Swiss dive bezel in our piece on the Deepstar bezel, or about the chronograph mechanism that sits beneath it in the column wheel. If you are weighing brands, our six-check guide to choosing a dive watch brand gathers the questions worth asking.
Where the term comes from
The watches came first. The label came later.
“Tool watch” entered watch journalism in the late 1990s, but the concept predates the term by decades. The Swiss makers who built these instruments in the 1950s and 1960s, Aquastar among a half-dozen serious competitors, never used the phrase. They sold professional watches.
The earliest Aquastar catalogue calls the Deepstar a chronographe-instrument, French for chronograph instrument. The English came later.
The distinction that matters
Tool watch, or tool-styled watch?
A real tool watch is qualified, by a military diving unit, a national space programme, a commercial saturation contractor, an offshore racing class, against a written specification it has to survive. A tool-styled watch borrows the aesthetic without ever having to pass the test.
The mid-century chronographs that travelled with NASA, the dive watches issued to the Marine Nationale’s combat swimmers, the regatta timers fitted to America’s Cup boats: those were tool watches. The fashion reissues that came later, beautifully made as they are, were not.
Aquastar is unusual in the canon because the brand never made a non-tool watch. There is no Aquastar dress watch, no evening piece, no precious-metal reference. Every watch shipped since 1957 has been a working instrument, dive, regatta, or aviation, and the brand sat out the 1990s quartz-fashion trend entirely.
How to tell
The three defining specifications.
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Measurable function
A dive watch needs a uni-directional bezel and 100 meters or better water resistance. A pilot’s watch needs an anti-magnetic case, because the cockpit is magnetised by the radio equipment, and a tachymeter or slide rule. A racing chronograph needs a fifth-second register and decisive pushers. The specifications are testable, not aspirational.
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Legibility under stress
Tool watches read in low light, through water, at speed. That drives high-contrast dials, oversized lumed markers, and bezel scales that work under glove operation. The Aquastar Benthos dial is semi-gloss black so it does not reflect divelight back at the user. That is a tool decision.
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Field serviceability
Tool watches are built to be serviced over decades, not thrown away. The Aquastar Benthos 500 II of 2023 still uses the same gasket pattern as the 1970 original, so a fifty-year-old Benthos can be re-sealed by the same workshop with the same parts.
Where it began
The 1959 Navigator.
The Aquastar Navigator was the first integrated analog dive computer sold to consumers. It replaced a diver’s separate gauges with one wrist instrument that read depth, computed no-decompression time, and laid the foundation for every Aquastar tool watch that followed.
Four tools, sixty years
One workshop, four kinds of work.
Each family below was built to do one job. None has changed family in sixty years.
Saturation diving
Aquastar Benthos.
The first Swiss dive watch rated to 500 meters, released in 1970. Listed in the U.S. Navy diving manual that same year. The modern Benthos Heritage II returns to the original case architecture.
Skin diving
Aquastar Model 60.
The 1957 cushion-case skindiver: 37 mm steel, 60-minute bezel. Don Walsh wore one on the bathyscaphe Trieste’s 1960 descent to Challenger Deep. The MKII Re-Edition is the same case, built in Bienne.
Aviation timing
Aquastar Airstar.
The 1965 Swiss pilot’s chronograph. Worn by Jacques Mayol and Philippe Cousteau. The 60th anniversary Re-Edition uses an exclusive Soigné-grade La Joux-Perret L113 column-wheel calibre.
Worn at work
Still on the wrist of working divers.
Modern commercial divers, surface-supply equipment, real conditions. The Aquastar Benthos in service today, the way the working diver has always carried Aquastar.
A tool is for life
Built to be serviced, not replaced.
Every Aquastar can be returned to the Switzerland workshop for service, vintage or modern. Movements are cleaned, regulated, pressure-tested, gaskets replaced. The international warranty covers two years; the workshop covers the lifetime of the watch.
Frequently asked
Tool watch questions, answered.
What defines a modern tool watch?
What defines a modern tool watch is not the styling but three testable properties. First, a measurable function tied to a working profession, a unidirectional bezel and 100 m-plus water resistance for a diver, anti-magnetic protection and a slide-rule or tachymeter for a pilot, decisive pushers and a 1/5-second register for a racing chronograph. Second, legibility under stress, so high-contrast dials, oversized lume, and bezel scales that read through gloves or water. Third, field serviceability, so a case designed to be opened and resealed for decades rather than replaced. A watch that passes all three has been designed for the job. A watch that borrows the aesthetic without passing the three checks is a tool-styled watch, not a tool watch. On an Aquastar Benthos the 1970 gasket pattern still fits the 2023 case, which is a working example of the third criterion.
What is a tool watch?
A tool watch is a watch designed and built for a purpose beyond simply showing the time of day. Aquastar pioneered the tool watch in diving: the brand transformed the time-only watch into a computing tool for the diver. The Aquastar Navigator (1959) led the innovations; the Deepstar bezel (1962) gave divers a way to read no-decompression time at a glance and is credited with saving lives; the Benthos added an elapsed-time bezel for the full dive plus a central chronograph hand to time the ascent stops. Every Aquastar model carries a tool function alongside the time-of-day function.
Is every Aquastar a tool watch?
Yes. From the Navigator in 1959 onward, every Aquastar has carried a tool function alongside the basic time read: the Deepstar dive chronograph (1962), the Benthos 500-meter saturation diver (1970), the Model 60 cushion-case skindiver (1957), the Airstar pilot's chronograph (1965). The brand has never made a non-tool watch.
What makes a Swiss tool watch different?
Aquastar founder Frédéric Robert filed eleven patents between 1957 and 1977 to add specific computing functions to the diver's wrist: the 1964 no-decompression bezel, the 1965 dual-gasket crown that made a serviceable 500-meter case possible, the 1966 improved bathymeter for the Cousteau-Comex saturation programmes. The 1970 Benthos was the first dive watch with an elapsed-time bezel for the full dive paired with a central chronograph hand for the ascent.
Which Aquastar was issued to the Marine Nationale?
The Benthos (third generation) was issued to French Navy combat divers based in Toulon from 1979 to 1984. Approximately 3,200 watches were procured during that six-year period.
Are vintage Aquastar tool watches still serviceable?
Yes. Every Aquastar can be returned to the Switzerland workshop for service, vintage or modern. Movements are cleaned, regulated, pressure-tested, and gaskets replaced. The international warranty covers two years; the workshop covers the lifetime of the watch.
Where are Aquastar tool watches made?
Aquastar tool watches are built in Bienne, Switzerland. The Deepstar, Benthos, Model 60, and Airstar Re-Editions are all assembled and serviced in the same workshop.
How is a tool watch different from a luxury watch?
A tool watch is built around a testable function: the bezel calculates decompression, the dial reads through water, the case survives a magnetised cockpit. A luxury watch may borrow the same aesthetic, but it is not designed to pass a procurement specification or a working dive.
When did the term tool watch become common?
The phrase entered watch journalism in the late 1990s, although the category predates the term by decades. The Swiss makers building these instruments in the 1950s and 1960s, Aquastar among them, called them professional watches. Early Aquastar catalogues describe the Deepstar as a chronographe-instrument.
What was the first tool dive watch?
The 1959 Aquastar Navigator is the first integrated analog dive computer sold to consumers, a wrist instrument that read depth and computed no-decompression time on the wrist. The 1962 Deepstar then brought the patented no-decompression bezel onto a dive chronograph, and the 1970 Benthos 500 added a central chronograph hand for timing the ascent.
