Seiko Prospex Turtle SRP777

The Seiko Prospex SRP777 is a 200m automatic dive watch introduced in early 2016, nicknamed the "Turtle" for the cushion-shaped case that revives Seiko's 1970s 6309 divers. It is the black-dial reference within the SRP77x launch series and runs Seiko's 4R36 automatic caliber. It measures 44.3mm across, carries a Hardlex crystal, LumiBrite markers, a unidirectional elapsed-timing bezel and a screw-down offset crown, and shipped on a silicone rubber strap.

The SRP777 belongs to the SRP77x series that Seiko launched in early 2016. Monochrome-Watches, reviewing the range at release, described the models as drawing directly on Seiko's cushion-cased 63XX divers of the 1970s — the 6309 line that ran through 1988 — and noted that the new watches keep "the same bezel font and layout as the original," with the cushion case as "the central vintage element that defines them." That cushion silhouette is the source of the enthusiast "Turtle" nickname.

Bespoke Unit frames the SRP777 as "a modern reissue of a Seiko diving icon first released in the '70s," reworked for a current buyer who wants the shape without the risks of the vintage market. Rather than a faithful copy, it is a reinterpretation: the general proportions and dial layout carry over while the internals and rating are updated.

The most concrete update is the depth rating. In its hands-on review, 60Clicks records that the SRP777 dial carries "an increased depth rating of 200 meters (up from 150m)" and the Prospex logo, alongside the switch to the hackable, hand-windable 4R36 movement. The result is a watch that reproduces the 1970s design language on a modernized platform.

The SRP777 runs Seiko's 4R36 automatic movement. Caliber Corner lists it with 24 jewels, a 21,600 bph (3 Hz) beat rate, roughly 41 hours of power reserve, and a day/date calendar at the 3:00 position; it both hacks and hand-winds. Seiko rates its accuracy at +45 / -35 seconds per day under normal wearing conditions.

Strapcode dates the caliber to mid-2011, introduced within the 4R3x family (35, 37, 38, 39). It describes the 4R36 as an upgrade of the earlier 7S-series movement, adding "hacking and hand-winding functionality, with addition of day/date display." This is the practical difference the SRP77x series gained over Seiko's long-running 7S26 divers such as the SKX line, which could neither hand-wind nor stop the seconds hand for precise setting.

Both references note the movement's wider identity: Seiko Instruments sells an unbranded equivalent, the NH36, to third-party and micro-brand manufacturers, so the 4R36 is effectively Seiko's own-brand version of that widely used caliber. The 4R36 differs from the sibling 4R35 only in adding the day complication; dimensions, jewel count and accuracy are otherwise shared.

Reviewers agree the SRP777 is large on paper but manageable in practice. Writing for Time+Tide, Felix Scholz notes that "at 44mm, it's a bit large, and with its heft it doesn't exactly disappear on the wrist," but adds that "the curves make it quite comfortable to wear." His main reservation was the bezel action: he wrote that he'd "love a bezel that felt a little crisper in hand," and found the supplied silicone strap "dug into my wrist a little," recommending the steel bracelet option instead.

60Clicks reaches a similar conclusion on fit, observing that "although relatively large at 44mm, its square 'cushion-case' design and squat lugs make it wear comfortably on all but the smallest of wrists." The same review rates the rubber strap more kindly, calling it "soft and pliable" and noting it fit well "on the third to last hole" of a 6.5-inch wrist.

Bespoke Unit's owner review agrees the watch wears smaller than its dimensions suggest: "in spite of its larger dimensions, the watch is a pleasure to wear," the reviewer writes, because it "lays relatively flat on the wrist" and the case "wears much smaller than it reads on paper."

The SRP777 was one of four references in the 2016 launch series. Monochrome's hands-on covered the SRP773K1, SRP775K1, SRP777K1 and SRP779K1 together, differentiated by dial and bezel treatments while sharing the cushion case, 4R36 movement and 200m rating; the SRP777 is the plain black-dial version.

Seiko later revised the Turtle. Exquisite Timepieces, comparing the SRP777 with the newer SRPE93, notes the SRPE93 grew to 45mm and dropped the SRP777's beveled day-date window to accommodate a lume pip added at the 3 o'clock marker for ISO dive-watch compliance. The case-back text also changed, from the SRP777's "Air Diver's 200m" to "Diver's Watch 200m."

The two generations share more than they differ. According to the same comparison, both use the 4R36 automatic with a 41-hour reserve, a 120-click unidirectional bezel, a matte black LumiBrite dial, 200m water resistance and a black silicone strap — the changes between them are largely about case size and meeting current dive-watch certification rather than a wholesale redesign.

Bespoke Unit lists the SRP777's retail price as $475 for the version on the silicone rubber strap. At launch it was sold through Seiko's authorized dealer network and specialist retailers; Long Island Watch, for example, cataloged it as the SRP777 / SRP777K1 on the standard silicone dive strap.

The SRP777 has since been discontinued. Exquisite Timepieces reports that it "averages around $400 on the secondary market," while the still-in-production successor, the SRPE93, "typically retails for approximately $495." Buyers cross-shopping the two are effectively choosing between the earlier beveled-window SRP777 on the used market and the current, ISO-configured SRPE93 at retail.

One recurring buying note across reviews concerns the strap. Time+Tide's reviewer found the OEM silicone strap uncomfortable and recommended paying the additional cost for Seiko's steel bracelet, which he rated as better quality — a common upgrade path for owners of the rubber-strap SRP777.