Islote means “small island” in Spanish but the dive site of that name off Cabo Pulmo, on Mexico’s Baja peninsula, is hardly more than a large guano-covered rock jutting out of the Sea of Cortez, buffeted by an endless march of waves. Our boat captain manoeuvres the small panga boat as close to the foamy chaos surrounding it as he dares and we prepare to splash in. I give a final puff on my regulator and nod at my dive buddy on the opposite gunwale before we simultaneously backroll into the water. Bobbing on the surface, I spin the bezel on my Seiko Prospex Marinemaster to align the zero mark with the minute hand and release the air from my buoyancy vest to descend.

Topside, Islote is not of much interest other than as a navigational hazard, but underwater is a different story. The 30m high rock pinnacle rises from a sandy bottom, an oasis in an otherwise featureless landscape that provides shelter for small reef fish and an anchorage for a colony of sea fans that wave hypnotically in the current. This outpost of sea life also draws schools of larger fish – jacks and barracuda – that come here to feed, and in turn the odd sea lion from the colony across the bay. Diving here allows the rare opportunity to observe the food chain from bottom to top. But here, the sea lion is not at the apex. That role is occupied by the bull sharks that cruise the perimeter of Islote.

2015 marked the 50th anniversary of the Seiko diving watch.
In 1965, the reference 62MAS debuted; it was a modest timepiece, not unlike the other diving watches of the era, with a narrow rotating bezel, thin lugs and a mere 150m of water resistance. While the watch was relatively unremarkable, it was the patriarch of what is arguably the finest, and most beloved, lineage of diving watches in history. Unlike Switzerland, which is as well known for its Alpine splendours as it is its watchmaking heritage, Japan is an island nation with a centuries-old tie to the sea and a history of diving. This heritage has not been lost on Seiko, whose diving watches have long had a reputation as true instruments more than collectables.

Seiko 62MAS
Seiko 62MAS

It’s a Gas

While most of Seiko’s dive watches have been targeted towards free swimming divers breathing from SCUBA (self-contained underwater breathing apparatus), a watch appeared in 1975 that saw its origins in the arcane world of commercial saturation diving. The 1960s saw a boom in offshore oil drilling and with that came a need for brave men who would work on the sea floor for days at a time, fitting and welding massive pipelines and drilling apparatus. Between stints in the water, the divers emerge into a dry “diving bell” that transports them to and from the surface, where they then live in a pressurised habitat and breathe a gas mixture that contains oxygen, nitrogen and helium.

This strange new working environment, aside from its effects on the body, also introduced a new challenge for watchmakers. As the divers decompressed at the end of their underwater stint, the tiny helium atoms that had penetrated their watches would expand and blow off the crystals. Some brands responded by building a one-way pressure relief valve into the watchcase. But Seiko had another solution – make the watch impervious to helium penetration.

The watch they built was the now legendary Marinemaster 600m, reference 6159-7010, which introduced numerous innovations like an L-shaped case gasket, monobloc titanium case, which was the first dive watch made from the material, and a unique shroud that protected the timing bezel from damage or accidental rotation. This last featured set it apart visually from every other dive watch and earned it the nickname “Tuna Can” for its similarity to the round tins in which the pelagic fish is sold.

Swimming with Sharks

Our group of four divers descended alongside Islote to the sand bottom and fanned out in a group facing away from the rock to scan for sharks. The colder Pacific waters here in the Sea of Cortez teem with plankton, the tiny creatures at the very bottom of the food chain. While plankton is the bedrock of the prodigious marine life, it also makes for murky water and limited visibility. Something primal in my brain awakened knowing that a toothy predator could be swimming mere feet away in the gloom and all my senses were alert. Then my eye caught movement and the familiar shape of a shark swam into view. The bull shark is well named, its bulk and blunt snout setting it apart from sleeker reef-dwelling sharks; they are also thought to have the highest levels of testosterone in the animal kingdom. My spine buzzed  with a fight-or-flight response. But the shark only circled us at a distance, swimming in and out of my vision. Then a second one appeared, and a third, all following in a wary circuit, eyeing us as cautiously as we did them.

The Marinemaster 1000m, reference SBDX011, is a direct descendant of that original Tuna Can and sits atop Seiko’s professional grade Prospex (“professional specifications”) line. Its water resistance has been increased from its predecessor’s 600m to a healthy kilometre, but otherwise it retains the same exotic aesthetics such as the oversized dial markers that glow with Seiko’s trademark brightness, the monobloc black titanium case, ceramic shroud and its extra-long vented rubber strap. That strap is a Seiko innovation also introduced in 1975 on the ref. 6159, and now found on countless dive watches from other brands. The accordion-like ripples in the strap allow for use over a thick diving suit when it is pulled tight. As water pressure compresses a neoprene sleeve, the strap vents contract, keeping the strap snug on the wrist.

Seiko SBDX011

Today’s diving watches have become more emblems of adventure than tools for it, thanks to the advent of the digital dive computer; accordingly, the appearance of most modern divers reflects this softened role. But the Marinemaster forgoes the polished look of so-called “desk divers” for a distinctly uncompromising aesthetic. On the wrist it sits tall and bulky and there isn’t a polished surface to be found. It more closely resembles any other wrist instrument a diver wears, such as a compass or depth gauge, than it does a wristwatch. While the current trend in watches favours transparent casebacks to view the workings within, not only does the Marinemaster 1000m eschew a clear caseback, it forgoes a separate caseback entirely, opting for a one-piece case in the service of optimum water resistance. To access the movement, a watchmaker must go in from the top, removing bezel, crystal and dial first. This watch is a case study in form following function.

High Calibre

Deep inside this watertight case, inaccessible and invisible to all but a few watchmakers with the right tools, is the Seiko Calibre 8L35. Despite Seiko’s milestone quartz, Kinetic and Spring Drive movements in recent years, this movement is a self-winding mechanical motor. It is no pedestrian movement like the sturdy tractors Seiko fits in thousands of its entry-level divers. The 8L35 is a less fussy version of the vaunted 9S55, a calibre from the high-end Grand Seiko line, built in the brand’s Morioka workshops. Its 50-hour power reserve is replenished by Seiko’s Magic Lever winding system, which requires the slightest of movement to tension the mainspring. The 8L35 is perfectly suited for a tool watch like the Marinemaster – it is unashamedly undecorated, but eminently rugged and functional.

When the bull sharks tired of us noisy bubble-blowing divers, they disappeared as quickly as they appeared. We warily turned back to the rock pinnacle, still scanning the waters for the predators we knew could see us even though we couldn’t see them. As we rounded the base of the rock, a shadow fell over us. Looking up I could see a massive vortex of silver jacks slowly turning in the current above. There must have been several thousand fish, enough to blot out the sun. This is the prolific sea life for which Cabo Pulmo is known. In the 1990s, after years of overfishing, the Mexican government declared the waters here a marine reserve. Now Cabo Pulmo is a case study for environmental management, with marine life populations growing over 400 per cent, the reason divers make the two-hour drive on washboard dirt roads to get here.

Seiko Calibre 8L35

We began a spiralling ascent of Islote, from sun into shadow and back again, pausing to examine the colony of elegant sea fans waving in the current and the tiny nudibranchs that live among the fronds. Rays of dappled sunlight penetrated the water, getting brighter as we ascended. I glanced at the Seiko on my wrist, its Lumibrite-painted markers glowing, and thought about the relevance of the diving watch in the computer age. Many dismiss the watch as an anachronism, an irrelevant extravagance to the modern diver. But tracking elapsed time is something the dive watch was designed to do from the start and still does better than any other instrument, including the dive computer. The latter tracks total dive time but for an on-the-fly read, such as for navigation, distance measurement or surface intervals, a spin of a bezel is still the best.

Near the top of the rock, I paused my ascent for a three-minute safety stop at 5m and set the bezel to align with the minute hand. The Marinemaster’s bezel is one of the best in the business. Perfectly positioned cutouts in the ceramic shroud allow for quick access, and the uni-directional ring ratchets with the precision of a bank safe. The oversized arrow-shaped minute hand leaves little doubt as to how much time has passed. Score one for analogue.

As I hung there counting down time, something in my peripheral vision startled me. It was a lone sea lion swimming above us, just below the surface. Islote is several miles from the sea lion colony on the mainland and this fellow seemed lost. He gave our group a sidelong glance as he swam lower in the water column, but his attentions were clearly elsewhere. He hung below us, stationary in the current, scanning the murky sea beyond the rock. Did he know about the trio of bull sharks out there? Was he planning to run the gauntlet to the mainland? The sweeping seconds hand counted down the final seconds on my three-minute stop and I ascended the last few metres to the surface, leaving the food chain below.