Hands-On We Put The Casio G-Shock 2500 Series "CasioNaut" Through Its Paces

Photos by Georgia Griffiths and Jack Shepherdson

So, to start: the 2500 series is a fully analog G-Shock featuring no screens, digital readouts or Bluetooth connectivity: just a two-handed central time display, a small seconds subdial and a date display. Prices also start at less than A$300 (not A$100,000+ like the recently-released "Blue Rose Project"!) However, this isn’t just a time-and-date watch. (More on that in a second.)

Firstly, it’s fitted with Casio's Shock Release Hand system (that debuted on the GA-V01 in April 2025), which holds the minute hand in place with magnets instead of a conventional mechanical post. Watch hands are particularly susceptible to impacts, and if this G-Shock takes a particularly big knock, the minute hand can absorb it and move with the force before snapping back into position. Should the hands ever get misaligned, the system also pulls them back into place within a few minutes.

This would be worth the price of entry alone, but what the leaked images didn't reveal is that Casio have also managed to squeeze an additional complication into the pure analog layout. This CasioNaut also has a stopwatch, and it’s one that operates like no other on the market, mechanical or quartz.

The 2500 debuts a brand new Casio quartz module, the 5757, that gives the date wheel a dual function: in standard mode, it reads the date, but cycle between the watch’s modes with the pusher at 8 o’clock, and it enters stopwatch mode. In this mode, the central hour and minute hands continue to tell time as normal, but upon activation, the small seconds hand resets to zero and the date wheel then cycles round to display ST (short for stopwatch), hidden one position behind zero. Start it with the pusher at 4 o'clock, and the seconds hand sets off, the date wheel clicks over to zero, and it now counts the stopwatch minutes.

This is really clever stuff, and it gives the CasioNaut a huge functionality boost without breaking its clean analogue layout with digital screens or a dedicated stopwatch subdial. When changing modes, the date wheel spins a little slowly, but it’ll go forwards or backwards to get to ST to always take the shortest path, and you can override it and start the stopwatch whilst it’s still working its way round.

The date wheel also plays an additional role when setting the calendar, which is perpetually calibrated to jump odd-length months and leap years. The number on the date wheel is used to cycle through and select the different positions of the year (e.g. 2 then 6 for 2026) before setting the month and date the exact same way. Again, clever, and keeps the dial uncluttered. In comparison to the CasiOak and its additional ana-digi display, the CasioNaut is positively sparse.

Whilst the watch internet has already ordained the CasioNaut as the spiritual successor to the CasiOak from leaked images alone, I actually see these watches as very different. The CasioNaut is far simpler than the CasiOak as it lacks the CasiOak’s alarm, world time, or countdown timer complications - if you’re comparing these two watches on pure functionality alone, there’s a clear winner. Instead, think of the CasioNaut as a simplified alternative to the CasiOak that delivers a stripped-down complications suite in a smaller case while similarly offering a familiar-to-watch-enthusiasts aesthetic.

Where you can see a proper ‘family resemblance’ to the CasiOak is in its bracelet, as it shares the same full-width link design that integrates to the case through a form-fitting, but non-articulating, endlink. Because this endlink on the CasioNaut is fixed, it can effectively be considered part of the watch head, which blows the lug-to-lug all the way out from 46mm to 57.5mm.

Whilst I like the look of the large monobloc link design, on the wrist, I’m less enamoured. It’s surprisingly loose by modern standards and features some quite substantial gaps between the links. I suspect it’s down to the way they connect, using standard spring bars instead of link screws or pin-and-collar fittings. This is another great feature and makes resizing as easy as strap changes, but if it's the reason for the loose bracelet, I’d honestly trade that convenience for screw-links and a tighter bracelet.

The clasp is also a disappointment. It’s a simple pressed-steel construction with only three points of micro-adjustment, which is especially egregious with such long links, and I just can’t quite get it to size correctly to my wrist. This is par for the course with G-Shock bracelets, though, and whilst they might have been up to scratch a decade ago, many microbrands have shown you can get higher quality bracelets (including ones with on-the-fly micro-adjust, a feature long overdue in the G-Shock catalogue) in the same price range.

Compared to my gripes with the bracelet, the dials are where the CasioNaut absolutely sings. The layout is perfect: horizontally aligned and excellently spaced, there’s minimal dial text and some fantastic attention to detail. The date wheel aperture, cut to show three numerals, features a beveled edge and central indicator, whilst the rest of the dial has applied hour indices with lume on just the hour and minute hands. With the models we’ve had for review, it looks like the full steel models take an additional step up in dial finishing over the resin models,. There are subtle variations between dials and finishes on different models.

The CasioNaut launches in a diverse lineup of colours and material combinations across the range. I’ve had the chance to test black and yellow examples in the classic G-Shock resin, a hybrid version in stainless steel on a resin strap, and a full steel on steel version with an integrated bracelet. The steel cases are a good look, but the resin cases are for getting stuff done, so I’ve put them to the test just like how you and I actually wear G-Shocks: as a running watch, and in the ocean.

I strapped on the yellow CasioNaut and hit the road, or rather, the trail. In short, it’s an exceptional running watch. It's high-contrast, it’s glanceable, and of course, sweat-proof. I found the yellow model provided the best legibility: the lume on the hands is decent but minimal, but the built-in light is useful for night runs.

The stopwatch is a game changer for a runner, though. I’ve run with a few mechanical analog chronographs over the years, and try holding a good pace and read your minutes off a tiny subdial - it’s impossible! The CasioNaut’s stopwatch function is different because it’s digital. Not like a screen, but like a digit; a number, so with a quick glance you know how long you’ve been at it. Excluding an LCD digital watch, I can’t think of another with a chronograph or stopwatch that gives a physically digital readout like this, and on a run, that’s seriously useful.

Testing it on a run is where the CasioNaut’s case dimensions also proved to be bang-on. Case dimensions differ between the steel and resin models (though only by a millimetre). The resin measures in at 44mm across with a 12mm thickness, whilst the steel is 43mm by 13mm. On paper, that’s a substantial watch, but because it tapers in above and below those protective ears to make space for the pushers, on the wrist, the CasioNaut feels smaller than most big, chunky G-Shocks. When you’re running, you want a watch that won’t get in the way and you can forget about, so top marks for Casio here.

Speaking of the case design, let’s address the Patek-shaped elephant in the room. Which ‘naut’ the already-established nickname references is up for debate. In the leaked photos, and when you look directly down on the 2500’s case, it admittedly resembles those famous Patek sports watches a little, but on the wrist, it’s entirely its own animal. It’s beefy, angular and has that classic G-Shock chunkiness that places it more in the tactical, functional school of design than the svelte world of a Patek Philippe. I think the watch community might be stretching with this nickname, but hey, I'm not here to kill anyone's vibes.

Taking the CasioNaut into the water, the digital stopwatch readout is just as legible through a set of goggles as when topside - but it’s also where I encountered this watch’s limits. Even with a 200-meter depth rating, you simply can’t use it as a dependable deep dive timing watch. When the stopwatch hits 31 minutes and 59 seconds, it stops, an obvious by-product of its dual function as a date display - there are no numbers on the wheel past 31. As much as I really like the CasioNaut, this is its Achilles heel - it massively kneecaps its functionality.

And here’s the kicker: there’s a simple solution right in front of Casio, and for a G-Shock that’s been developed with such foresight and clever thinking, to have missed it drives me a little mad. With any mechanical two-register chronograph where the minutes subdial only times up to 30 minutes and there’s no hours subdial, you keep track of the 30-minute blocks yourself. If the CasioNaut were to do this and just skip the 31st minute, reset to zero after half an hour and keep running, you’d be able to count those 30-minute blocks in your head to time longer events, like a dive or a longer run. As it stands, the CasioNaut is only good for a five-kay.

Obviously, if you’re scuba diving, you don’t want to be relying on doing underwater arithmetic when it’s life or death anyway, but for keeping track of how long you’ve been snorkelling, swimming laps, running, or just when your parking meter expires, such a small change would have made this Casio so much more capable. You also can’t use the pushers whilst submerged, so restarting the stopwatch whilst underwater isn’t an option.

I’ve also got an axe to grind with the backlight. It shines charmingly from a small 80s-style orange LED,  but it shines from a gap in the rehaut between the 6 and 7 o’clock markers. The problem is that those markers are so tall that they cast a shadow that blocks the light from reaching the right side of the dial. Its location just feels like an afterthought, especially when it can’t even illuminate its brand-new stopwatch complication. Its brightness also depends heavily on the dial colour and is less useful on darker dials, so if legibility is your goal, go for the yellow CasioNaut.

If it sounds like I’ve soured on this new G-Shock 2500 already, that’s certainly not the case, as I’ve really fallen for this watch. The CasioNaut is so good that it’s hampered by the law of diminishing returns: when something is this close to perfect, the small flaws get magnified. Despite the little misses that I hope would be simple for Casio to update in a facelift down the line, I won’t be wasting a minute in snapping up a CasioNaut for myself - it’s one of the best G-Shocks releases in years.

Brand: Casio G-Shock
Model: 2500 Series (“CasioNaut”)
References Tested: GAC-2500 (resin), GMC-2500 (steel/resin hybrid), GMC-2500D (steel case and bracelet)
Diameter: 43mm (steel), 44mm (resin)
Thickness: 13mm (steel), 12mm (resin)
Lug-to-Lug: 46mm (steel), 43.5mm (resin), 57.5mm (including fixed bracelet endlink)
Case Material: Resin or stainless steel
Dial Colour: Various
Lume: Hands only, LED backlight
Water Resistance: 200 meters
Strap/Bracelet: Integrated resin strap with pin buckle or stainless steel bracelet with folding clasp

Quartz Module: QW-5757
Functions: Hours, minutes, seconds, date and stopwatch
Power Reserve: Approx. 2 years
Additional Details: Shock Release Hand system

Price: A$289 (resin), A$459 (steel/resin hybrid), A$599 (full steel)
Availability: From 7 November 2026
Limited Edition: No

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