Case #761 — Longines Hydroconquest 39MM Blue Ref. L3.779.4.96.6

Case #761 — Longines HydroConquest 39 mm "Blue Lacquer"

Ref. L3.779.4.96.6

Status: Available

Condition: Very Good Pre-Owned

Scope: Box, Papers, and Cards

Year: 2026

🔎 Case Notes

The HydroConquest has long been the watch a collector recommends when someone asks for a serious Swiss diver without the waiting list. The 2026 revision sharpened it considerably, and this is the reference at the centre of that update: the deep blue, 39 mm, steel-bracelet version — Ref. L3.779.4.96.6.

What you notice first is the dial. Longines specifies it as blue lacquered polished, with Swiss Super-LumiNova®, and in person it behaves like a mirror — flat and dark in shade, saturated and almost liquid under direct light. The revised design drops the Arabic numerals entirely in favour of applied indexes, with silvered polished hands and a date display, which is a meaningful change in character: this generation reads cleaner and more grown-up than the HydroConquest many collectors remember. A matching blue ceramic unidirectional bezel carries the tone around the case.

The 39 mm case is the reason this reference matters to a lot of buyers. Lug-to-lug is 48.10 mm and thickness 11.70 mm — compact proportions for a watch rated to 300 metres with a screw-in crown and screw-down case back.

This example dates to 2026 and is graded Very Good Pre-Owned. It has clearly been worn: there is wear throughout, of the kind consistent with reasonably careful daily use. The crystal and the ceramic bezel are clean. The case sides and the bracelet are where the evidence of wear is concentrated. It comes with its Box, Papers, and Cards, and the bracelet is currently sized to fit an approximately 8-inch wrist.

🕰️ The Evidence

• Reference: L3.779.4.96.6
• Model / Collection: Longines HydroConquest, 39 mm Automatic
• Year: 2026
• Case: Stainless steel
• Case Diameter: 39.00 mm
• Thickness: 11.70 mm
• Lug-to-Lug: 48.10 mm
• Lug Width: 20 mm
• Dial: Blue lacquered polished, applied indexes with Swiss Super-LumiNova®, silvered polished hands
• Crystal: Scratch-resistant sapphire with anti-reflective coating on both sides
• Bezel: Blue ceramic, unidirectional rotating, 60-minute dive scale
• Crown: Stainless steel, screw-in
• Caseback: Solid, screw-down
• Movement: Longines Calibre L888 (L888.5), self-winding mechanical
• Frequency: 25,200 vibrations per hour
• Balance Spring: Monocrystalline silicon
• Power Reserve: Up to 72 hours
• Functions: Hours, minutes, seconds, date
• Water Resistance: 30 bar (300 metres)
• Bracelet: Stainless steel three-link ("H-link") bracelet
• Clasp: Double security folding clasp with micro-adjustment system
• Bracelet Fit: Approximately 8-inch wrist
• Condition: Very Good Pre-Owned — wear throughout consistent with reasonably careful use; crystal and ceramic bezel clean; case sides and bracelet show wear
• Factory Warranty: Longines applies a five-year warranty on mechanical watches purchased from January 1, 2021; as a 2026 example this should remain within that period, subject to the exact warranty-card activation date and Longines' warranty terms
• Included: Box, Papers, and Cards

🌟 Collector Provenance

The HydroConquest occupies a specific and well-understood position in modern collecting: it is the entry point into genuinely capable Swiss diving watches from a house with real nineteenth-century credentials, built to a specification that does not apologise for its price point. A 300-metre case, a screw-in crown, a ceramic bezel and an in-house-exclusive automatic calibre is a specification sheet that would have been remarkable a decade ago at any money.

The 2026 generation is the one enthusiasts had been asking for. The redesign follows the direction introduced with the HydroConquest GMT in 2024, which revised the collection's dial layout and finishing. The numerals are gone, the dial is lacquered and polished rather than textured, and the whole watch reads as a more considered object. For collectors who admired the HydroConquest's value but found the earlier dials busy, this is the generation that resolves the objection.

The 39 mm case is the other half of the story. The HydroConquest has historically been a 41 and 43 mm watch, with the collection's identity built around a certain amount of presence. Offering the modern design in 39 mm — at 48.10 mm lug-to-lug and 11.70 mm thick — brings it into the proportions that have dominated collector conversation for several years, and does so without reducing the depth rating.

🌟 Technical Provenance

The calibre is the quiet argument for this watch. The L888 is a self-winding mechanical movement beating at 25,200 vibrations per hour, with a monocrystalline silicon balance-spring and a power reserve of up to 72 hours. The silicon hairspring is not a marketing flourish: silicon is light and corrosion-resistant, unaffected by temperature, magnetic fields and atmospheric pressure, and those properties improve a watch's precision and longevity.

Longines was confident enough in that technology to put its warranty behind it. The brand extended its warranty on all models equipped with a silicon balance-spring to five years, valid for automatic models purchased after January 1, 2021 — placing Longines alongside brands such as Rolex and Omega on warranty length.

The practical consequence is a three-day power reserve. Take the watch off on Friday evening and it is still running, and still on the correct date, when you reach for it on Monday morning. For an automatic watch that will share wrist time with others, that matters more than almost any other specification.

🧾 From the Case File

This is a diver sized for people who actually want to wear a diver every day. At 39 mm across, under 12 mm thick and with a 48.10 mm lug-to-lug span, it sits inside a shirt cuff and will suit wrists that find a 42 or 43 mm case overbearing — while still delivering 300 metres of water resistance behind a screw-in crown and screw-down case back.

The bracelet is a genuine convenience advantage. Longines fits a stainless steel bracelet with a double security folding clasp with micro adjustment system, which means the fit can be corrected on the wrist as the day warms up or after swimming, without tools and without a half-link compromise. It is currently sized for an approximately 8-inch wrist.

Buying this example rather than a new one has two specific attractions. First, it arrives complete with Box, Papers, and Cards, which is the configuration collectors want on a modern reference. Second, as a 2026 watch it should carry a meaningful balance of Longines' five-year mechanical warranty, subject to the activation date recorded on the card and to Longines' terms — so the usual trade-off of pre-owned buying, losing factory coverage, is substantially reduced here.

The honest counterpoint is condition. This is a Very Good Pre-Owned watch, not a near-new one. The case flanks and the bracelet show wear from regular use. What has survived best is what is most visible head-on: the sapphire crystal and the blue ceramic bezel are clean, so the watch presents well from the top down. If you intend to wear a diver as a diver, that distribution of wear is arguably the right way round.

🗝️ BST Verdict

The reference that fixed the two things collectors used to raise about the HydroConquest: the dial is now clean, lacquered and numeral-free, and the case is 39 mm. The specification underneath it — 300 metres, ceramic bezel, silicon balance-spring, 72-hour calibre — has not been softened to achieve either.

A worn but well-kept 2026 example, complete with Box, Papers, and Cards, very likely still inside Longines' five-year mechanical warranty window, and sized for an approximately 8-inch wrist. Honest marks on the case sides and bracelet; clean where you look first.

👉 Every case deserves a closer look.