Case #757 — Longines Hydroconquest Green 42MM Ref. L3.788.4.06.6

Case #757 — Longines HydroConquest 42 mm, Green Dial and Ceramic Bezel

Ref. L3.788.4.06.6

Status: Available

Condition: Excellent Pre-Owned

Scope: Box, Papers, and Cards — warranty card undated, accompanied by the original purchase receipt

Year: 2026

🔎 Case Notes

Green is the colour that divides a room, and Longines has committed to it completely here: a lacquered, polished green dial sitting beneath a matching green ceramic bezel insert, with silvered polished hands and applied indexes cutting across the surface. In daylight the lacquer reads deep and glossy; in shade it closes down toward near-black. It is a louder choice than the familiar blue or black HydroConquest, and it wears with far more presence than the specification sheet suggests.

What makes this particular example worth a second look is its timing. The HydroConquest received its most significant update in nearly two decades for 2026, bringing a ceramic bezel and new dial options to Longines' flagship diver. This is a 2026 piece from that redesigned generation — a current-production reference, bought new and lightly worn, rather than an older steel-insert model.

Condition is graded Excellent Pre-Owned, with no specific flaws recorded at inspection. It arrives as Box, Papers, and Cards. The warranty card itself is undated, but the original purchase receipt accompanies the watch and establishes the purchase date — a useful piece of paperwork on a watch still young enough for the factory warranty period to matter.

The bracelet is presently sized to fit an approximately 8-inch wrist, with the factory clasp micro-adjustment available for fine tuning.

🕰️ The Evidence

• Reference: L3.788.4.06.6 (L37884066)
• Model / Collection: Longines HydroConquest 42
• Year: 2026
• Case: Stainless steel, screw-in crown, screw-down caseback
• Case Diameter: 42.00 mm
• Thickness: Approximately 11.7 mm
• Lug-to-Lug: Approximately 51.2 mm
• Lug Width: 21 mm
• Dial: Green lacquered polished, applied indexes, silvered polished hands, Swiss Super-LumiNova®
• Crystal: Scratch-resistant sapphire with several layers of anti-reflective coating on both sides
• Bezel: Green unidirectional rotating bezel with ceramic insert, luminous capsule at the zero marker
• Movement: Longines Calibre L888.5, automatic
• Movement Type: Self-winding mechanical, 25,200 vibrations per hour, monocrystalline silicon balance-spring
• Power Reserve: Up to 72 hours
• Functions: Hours, minutes, seconds, date at 3 o'clock
• Water Resistance: 30 bar (300 m)
• Bracelet: Stainless steel three-link bracelet
• Clasp: Double security folding clasp with micro-adjustment system
• Bracelet Fit: Approximately 8-inch wrist
• Condition: Excellent Pre-Owned — no specific flaws recorded at inspection
• Factory Warranty: Longines five-year manufacturer warranty — remaining coverage subject to the purchase date shown on the accompanying original receipt and to Longines warranty terms
• Included: Box, Papers, and Cards (warranty card undated), plus original purchase receipt

🌟 Collector Provenance

The HydroConquest has occupied an unusual position in the market for close to twenty years: the Swiss diver that keeps turning up on shortlists where the alternatives cost considerably more. It has long been one of the standard recommendations for buyers seeking a credible Swiss diver in the lower four-figure range, and Longines has steadily upgraded the line rather than resting on it.

The 2026 generation represents the most thorough rework the collection has seen. After almost two decades, Longines rolled out what amounts to the most significant update in the model's history — a more modern design language without abandoning the collection's value proposition. Ceramic replaced the aluminium and steel inserts that defined earlier generations, and the dial range expanded; green is one of the configurations that arrived with this redesign rather than being carried over.

For collectors tracking the line's development, that matters. Earlier HydroConquest references are plentiful on the secondary market, but they are visually and technically a different watch — different bezel material, different case proportions, different dial treatments. A dated 2026 example documents the beginning of the current chapter rather than the end of the previous one.

🌟 Technical Provenance

The calibre is the quiet argument for this watch. The L888.5 is a self-winding movement with a silicon balance-spring and components that make it up to ten times more resistant to magnetic fields than the ISO 764 standard requires, with a power reserve of up to 72 hours. Silicon is non-magnetic, requires no lubrication at the balance spring, and is unaffected by the magnetic fields that surround laptops, speakers, phone cases and clasps — exactly the environment a daily-worn watch actually lives in.

The jump from roughly 65 hours to 72 hours of reserve across the L888 family is directly associated with the silicon balance-spring generation, which in practice means a watch set down on Friday evening is still running on Monday morning. For a rotation watch rather than a sole daily wearer, that is a genuine convenience rather than a specification-sheet flourish.

Around the movement, the case does the conventional dive-watch work properly: 300 m water resistance, unidirectional bezel, screw-in crown and screw-down caseback. The sapphire is treated with anti-reflective coating on both surfaces, which is why the lacquered green dial reads as cleanly as it does under direct light.

🧾 From the Case File

At 42 mm the case sounds large, but the 51.2 mm lug-to-lug and roughly 11.7 mm thickness keep it closer to the wrist than the diameter implies — the lugs turn down, and the profile slides under a cuff more readily than most 300 m divers. On an 8-inch wrist, where this bracelet is currently sized, the proportions are comfortably within range.

The clasp deserves mention: the double security folding clasp includes an integrated micro-adjustment, so seasonal swelling can be corrected without tools or a trip to a watchmaker. Combined with the 21 mm lug width, the watch is also straightforward to put on rubber or NATO for summer use if a buyer wants a second look.

The practical case for this example over a new one is paperwork and condition. It is a current-production reference in Excellent Pre-Owned condition with no recorded flaws, it carries its box, papers and cards, and the original receipt pins down the purchase date that the undated warranty card does not — which is what determines how much of the five-year Longines coverage remains.

Buy with Confidence

BST guarantees the authenticity of every watch we sell and provides a 30-day mechanical performance guarantee under normal use.

Accuracy may vary with age and service history, and water resistance is not guaranteed unless specifically stated and pressure-tested.

🗝️ BST Verdict

A 2026-generation HydroConquest in the configuration that best justifies the redesign: lacquered green dial against a green ceramic bezel, on steel, with the silicon-balance L888.5 doing serious work behind a screw-down caseback.

Excellent Pre-Owned, complete with box, papers and cards, and documented by its original receipt — a current reference bought new, worn carefully, and presented honestly.

👉 Every case deserves a closer look.