Dive Watches: Does High Water Resistance Necessitate a Chunky Case?

One Friday afternoon, Sam and I were discussing the latest Marinemaster collection from Seiko. We compared the earlier editions of the Marinemaster with the monocoque case which was a lot thicker and the question pops. “Does a watch with high water resistance always require a thicker case?” As you go throughout your watch collecting journey, you will note that a watch with higher water resistance usually, but not always, yields a thicker case. Sam's response was “Great question. Go write on it” so here I am.

Meguro vs Seiko Thickness Comparison

To tackle this question, we first need to understand the concept and history of water resistance in horology. A water-resistant watch is designed to withstand exposure to water to a certain depth, usually indicated by the watch's rating (e.g., 30m, 50m, 100m, 200m, etc.). Also known as “waterproof” back in the days. As such, it is known as an interchangeable term.

Seiko 4299m Depth Test (Photo Credit: WatchesbySJX)

What most people do not understand is that the water resistance stated is the amount of pressure a watch can handle when it is static. Introducing movements dramatically increases the risk of water damage. Knowing this, it is advised that watches interact with water way above the stated amount. Especially when design elements such as a screwed in crown and caseback are absent, it raises more suspicion on the amount of water pressure it can withstand.

Marine Navy Operations (Photo Credit: Pinterest)

Historically, the importance of water resistance in watches became crucial during wartime, where exposure to water could easily damage the delicate movements and dials of timepieces. Soldiers, sailors, and adventurers required watches that could endure harsh conditions, including rain or immersion in water, whilst maintaining pinpoint accuracy. This led to advancements in watch technology, pushing manufacturers to develop timepieces capable of withstanding moisture, which naturally paved the way for the creation of more specialized models—particularly dive watches—designed to operate safely under the demanding conditions of underwater exploration and sports.

In the early days, brands pushed the limits of water resistance to provide reliable time trackers for divers, whose safety relied on precise timekeeping. Scuba diving typically required tracking time at depths of around 50 meters, where managing nitrogen absorption became crucial. However, as deep diving exploration and specialized expeditions, such as those conducted by Comex (Compagnie Maritime d'Expertises), advanced, the need for even greater water resistance emerged. These deep dives exposed divers to much greater pressures, pushing the limits beyond 50 meters, sometimes reaching depths of 150 meters or more. With these depths came increased risk, as failure to properly track time could result in decompression sickness (the bends), which could lead to paralysis or even death. As a result, the diving community began demanding watches that could withstand deeper pressures, ensuring divers could safely manage decompression stops and avoid life-threatening consequences.



1000m+ Water Resistance

Seiko Prospex Professional 1000M Tuna Ref. SBBN047

We start off big, looking at some watches with over 1000m of water resistance and their quirks. 1986, the Seiko Prospex 7C46-7009 AKA “Golden Tuna” is a grail for any watch collector out there. It was one of Seiko’s first few divers that challenged the big names with a watch that can reach a depth of 1000m of water resistance. It features a high end quartz movement, L-shapre gasket and titanium monocoque casing. It measures 49.6mm in diameter with a thickness of 16.1mm. Named after the resemblances to a tuna can, this is one of Seiko most iconic divers till today.

Squale Master Titanium 120ATM 65th Anniversary

Our next challenger up on this list for comparison is a recent 2024 release, the Squale Master Titanium 120ATM. Squale is a brand firmly rooted in the golden era of watchmaking and for it’s recent anniversary, they brought back the beloved 120 Atmos with the iconic “Von Büren Case”. It measures 42mm in diameter with a thickness of 16.15mm. A direct comparison with the Golden Tuna, we can see a smaller diameter with a similar thickness. With a key difference of Tuna is powered with a quartz movement whilst the 120 Atmos is powered with the SW200-1 automatic movement. Showing recent innovations and technology allowing for an automatic watch to boast a similar water resistance and thickness as previous quartz models.

Rolex Oyster Sea-Dweller (Photo Credit: Analog/Shift)

Not stopping there, we go all out with the iconic Rolex Oyster Perpetual Sea-Dweller released in 1967. Rolex played a huge role in stepping up to the challenge to design a watch to tackle the tough pressures of the deep ocean. The Sea-Dweller is amazingly waterproof at up to a depth of 1220m. Made possible with a helium escape valve, it poses a diameter of 43mm with a thickness of 17mm. Seeing this watch made it’s appearance in 1967, it boasts more impressive underwater capabilities with similar dimensions all whilst being fully automatic. It is clear to see the credentials behind Rolex reputation being ever solid. Refined editions has been made since then, bringing the thickness down to 15.1mm. Posing the question, could other brands do the same today?



300m Water Resistance

Seiko 62MAS (Photo Credit: Analog/Shift)

Moving on to the 300m range, in 1967 Seiko introduced the 6215-7000 (62Mas). Little did they know this professional dive watch will go on to make history, making waves as one of the most iconic dive watches till date. Serving as the foundation for what will be the Marinemaster series, the 6215-7000 was the first Seiko Diver that had 300m of water resistance. Powered automatically, it measures 44mm in diameter and 14mm in thickness, the 300m range of dive watches definitely boast slimmer dimensions.

Omega Seamaster Diver 300m (Photo Credit: Analog/Shift)

The next contender is a watch which will be later known as the “Bond Watch” is the 1967 Omega Seamaster 300. The Omega Seamaster Diver was later worn by James Bond in Goldeneye, becoming an instant cult classic which coined the nickname “Bond Watch”. The 1967 watch bears 300m of water resistance with 41mm in diameter by 13mm thickness powered by 552 self-winding calibre. Boasting similar water resistance as the 62mas, the Seamaster is able to cut down on the dimensions noticeably.

Rolex Oyster Perpetual (Photo Credit: thetruthaboutwatches)

Finally, when you think about 300m and diver, what watch comes to your mind? To me, it is the black diver with white markers, the Rolex Submariner, which speaks volumes on the branding Rolex has done throughout the years. The Rolex Sub boasts 300m of waterproof specs. But this was not always the case, when the Submariner first released in 1953, it boasted 100m (37mmx12mm) of depth rating which increased to 300m (41mm x 12.3mm) in 1979. With an increase of depth rating with minimal changes to thickness, we can see leaps in waterproof capabilities in the Submariner line (In part due to the diameter changes). We can clearly see a trend with dimensions and water depth rating being directly correlated in these examples. What varies is the ability and efficiency of brands to achieve much more in terms of water depth without more increases to dimensions. 

Squale 2001 Sand

Problems

Here comes the huge dilemma in watches. With vintage models and deep divers having such thick and chunky dimensions, would it still be appealing in today’s market. If your answer is yes, it is a fair point as these pieces have such historic value. Take for example the 62mas line where the DNA of the iconic diver has branched out to many of the Seiko Prospex Divers we see today. Their heritage holds a heavy amount of weight, especially for collectors whom have been in this hobby for a long time.

Seiko Case Finishing

Opposingly, if your answer is no, it is a fair point as well. Who would want to wear a 14.5mm plus thick watch around. It would be too heavy and inconvenient for most people, making it less practical. For many collectors and watch enthusiasts, a thinner, more refined watch is often preferred, as these models are seen as more versatile, stylish, and comfortable for daily wear. Simply put, while the historical value is undeniable, the appeal of ultra-thick, bulky dive watches has diminished, as they’re not considered “sexy” or wearable for most people today.

That said, why don’t all brands shoot for that universal sizing like the modern Rolex submariner? It has great water resistance, it wears fantastically, it has a great balance in dimensions. But why don’t other brands (Even Tudor) do it as well? We look at 2 main reasons:

1. Heritage
Many times, the appeal of re-releases of vintage inspired models is the story and more critically, the experience they bring back. If I were to give you a Seiko Tuna today that was 12mm thick with a good enough 300m of water resistance, would you even call it a Tuna? In addition to design, the specifications, dimensions, and capabilities are key factors that define the watch. To strip that away could make the re-release meaningless.

2. Identity
While the Submariner may be one of the most perfectly balanced dive watches, it’s not necessarily a template for every brand to follow. Each brand has its own identity, and part of that identity lies in offering something unique—design, features, or specifications that set them apart from the crowd. Following a "cookie-cutter" approach risks diluting what makes each brand special.

Seiko Tuna on Wrist

Watches walk a fine line between embracing modern trends and staying true to their core identity. While there’s certainly room for innovation—brands like Seiko, for instance, have a lot to offer in terms of evolving dimensions—too much change could risk losing what makes Seiko uniquely Seiko. Altering their dimensions too drastically might strip away the very essence of the brand that has defined it over the years. Balancing tradition with modernity is key to maintaining the brand's character while appealing to today’s tastes.



Today Context

With advancements in technology, the reliance on dive watches has become minimal in professional diving. Instead, dive watches have transformed into collectibles, status symbols, and potential indicators of watchmaking quality. The relentless pursuit of ever-deeper depths has faded into history, and today’s divers prioritize wearable dimensions while striving to maintain (or at most, slightly reduce) water resistance. Of course, vintage collectors still favor the designs and dimensions from the golden age of diving, and brands continue to take these inspirations into account. We often see reimagined versions of classic models with modern upgrades, typically paired with more practical, lower water resistance ratings.

Hitori Meguro Fuyu White & Aki Koyo

Looking at Grand Seiko divers, they’ve curated beautifully crafted pieces, with the SLGA015 being a prime example. This watch embraces the timeless, iconic design of a black dial with white markers, but with a unique Grand Seiko twist, featuring their signature spring drive movement and breathtaking dialwork. With a diameter of 43.8mm and a thickness of 13.8mm, the SLGA015 keeps dimensions relatively close to the Marinemaster, yet it sits comfortably on the wrist despite these numbers. Still, there’s a segment of collectors who long for a slimmer alternative in the iconic Grand Seiko diver’s lineup.

Brands with more flexibility, like Hitori, have curated the Meguro series, drawing clear inspiration from Grand Seiko but offering a fresh perspective. Hitori understood the pain point of the Grand Seiko divers, presenting a slimmer option at 12.5mm thick, albeit with a reduced 150m water resistance—a fair trade-off for many collectors.

It’s fascinating to watch the evolution of dive watches over the years and see how the diverse watch community continues to yearn for different aspects, whether it’s dimensions, design, or functionality. This constant pursuit of the perfect design has created an endless space for brands to share their creativity and vision, leading to unique takes on the dive watch. As the practical demand for dive watches decreases due to technology, part of me still wonders: if brands continued to push the boundaries of depth, what would they be able to accomplish today?