Longines HydroConquest vs Tudor Black Bay 58
Longines Hydroconquest L3.780.4.56.6 vs Tudor Black Bay 58 7939A1A0NU-0001, compared on the specs each brand publishes.
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The short answer
Two steel automatic divers of similar size, compared on published specs.
- Thickness: the Longines Hydroconquest L3.780.4.56.6 is 0.5 mm thicker (12.2 mm vs 11.7 mm).
- Water resistance: the Longines Hydroconquest L3.780.4.56.6 is 100 m more (300 m vs 200 m).
- Power reserve: the Longines Hydroconquest L3.780.4.56.6 is 7 hours longer (72 h vs 65 h).
- Calibre: Longines Hydroconquest L3.780.4.56.6 has L888.5; Tudor Black Bay 58 7939A1A0NU-0001 has MT5400-U.
- Certification: only the Tudor Black Bay 58 7939A1A0NU-0001 is listed as a METAS Master Chronometer.
Side-by-side specs
| Spec | Longines Hydroconquest L3.780.4.56.6 | Tudor Black Bay 58 7939A1A0NU-0001 |
|---|---|---|
| Case diameter | 39 mm | 39 mm |
| Thickness | 12.2 mm | 11.7 mm |
| Lug-to-lug | 48.1 mm | Not published by Tudor |
| Lug width | 19 mm | 20 mm |
| Calibre | L888.5 | MT5400-U |
| Movement | Automatic | Automatic |
| Power reserve | 72 h | 65 h |
| Water resistance | 300 m | 200 m |
| Crystal | Sapphire | Sapphire |
| Case material | Stainless steel | Stainless steel |
| Ships on | Bracelet | Bracelet |
| Weight | 166.1 g | Not published by Tudor |
| US list price | $2,000 (US list) | Not stated |
| Dial | Sunray black | Matt black |
| Certification | Not stated | METAS Master Chronometer |
| Status | In production | In production |
| Suits wrists of about our sizing guide | 16.2–17.4 cm | 15.5–17.4 cm |
Specs summarised in our own words from the brand's product pages: L3.780.4.56.6 source (checked 3 Nov 2026) 7939A1A0NU-0001 source (checked 3 Nov 2026). "Not published" means the brand page we checked doesn't list it, so we leave it blank rather than guess.
All the differences
- Thickness: the Longines Hydroconquest L3.780.4.56.6 is 0.5 mm thicker (12.2 mm vs 11.7 mm).
- Water resistance: the Longines Hydroconquest L3.780.4.56.6 is 100 m more (300 m vs 200 m).
- Power reserve: the Longines Hydroconquest L3.780.4.56.6 is 7 hours longer (72 h vs 65 h).
- Calibre: Longines Hydroconquest L3.780.4.56.6 has L888.5; Tudor Black Bay 58 7939A1A0NU-0001 has MT5400-U.
- Certification: only the Tudor Black Bay 58 7939A1A0NU-0001 is listed as a METAS Master Chronometer.
- Lug width: Longines Hydroconquest L3.780.4.56.6 has 19 mm; Tudor Black Bay 58 7939A1A0NU-0001 has 20 mm.
- Features: only the Longines Hydroconquest L3.780.4.56.6 has a date.
Wrist fit
Lug-to-lug decides overhang more than diameter does. Enter your wrist to see how each one should wear.
- Longines Hydroconquest L3.780.4.56.6 –
- Tudor Black Bay 58 7939A1A0NU-0001 –
Same rule of thumb as Watch Finder: case diameter of about 23.5% of your wrist circumference (−2 mm to +2.5 mm), and lug-to-lug no longer than about 29% of it plus 1 mm. A guide, not a rule; flat or round wrists differ.
Strap fit
The Longines Hydroconquest L3.780.4.56.6 has 19 mm lugs. The Tudor Black Bay 58 7939A1A0NU-0001 has 20 mm lugs. A strap bought for one won't fit the other. Size charts: Longines lug width chart · Tudor lug width chart.
Which should you buy?
It is the more compact case on paper (39 mm across). Our sizing guide puts it at about 15.5–17.4 cm.
It has the higher water-resistance rating: 300 m vs 200 m.
It is the slimmer case at 11.7 mm.
Prices and where to buy
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More: All Longines Conquest references · All Tudor Black Bay 58 references.
Questions
Which is bigger, the Longines Hydroconquest L3.780.4.56.6 or the Tudor Black Bay 58 7939A1A0NU-0001?
Per the brands, the Longines Hydroconquest L3.780.4.56.6 is 39 mm across and the Tudor Black Bay 58 7939A1A0NU-0001 is 39 mm.
Which is more water-resistant?
Longines Hydroconquest L3.780.4.56.6: 300 m. Tudor Black Bay 58 7939A1A0NU-0001: 200 m.
Have you tested these watches?
No. This comparison uses brand-published specs and our own analysis of them, not hands-on testing.
Watch.co is independent and not affiliated with any brand. We haven't handled these watches for this page: everything here comes from brand-published specs and our own analysis. Brand names are used only to identify products.