Wear a smartwatch with your Longines HydroConquest

Wear a smartwatch with your Longines HydroConquest

Smartlet is compatible with the Longines HydroConquest. Lug width: 18mm / 19mm / 21mm / 22mm - natively supported with no adapter. Installation uses the standard spring-bar system. No modification to the watch required. Fully reversible in seconds.
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Longines HydroConquest compatibility

Wear a smartwatch with your Longines HydroConquest

In short Smartlet is compatible with the Longines HydroConquest. Lug width: 18mm / 19mm / 21mm / 22mm - natively supported with no adapter. Installation uses the standard spring-bar system. No modification to the watch required. Fully reversible in seconds.

The HydroConquest is Longines at its most direct. Swiss manufacture movement, 300m water resistance, ceramic bezel, and a price that remains justifiable. The L888 calibre - developed in-house at Saint-Imier - runs at 25,200 vibrations per hour with 64 hours of power reserve. The 41mm in ceramic black or blue bezel has become one of the most recommended entry-level Swiss dive watches on the market. The recommendation holds because the watch delivers. Smartlet completes it.

Wear yours How it works
The problem
Choosing between health data and horological heritage every morning.
The solution
Smartlet One replaces your Longines HydroConquest's strap via the standard spring-bar system and positions your smartwatch on the same wrist. Both watches run simultaneously, with no modification to the watch and full reversibility in seconds.
Model
Longines HydroConquest
Lug width
18mm / 19mm / 21mm / 22mm
References
29covered
Reversible
In seconds

Choose your edition

One mechanism. Three personalities.

Every Smartlet One includes the dedicated adapter for your wearable. Pick the finish that matches your style.

Smartlet One - Shadow - Smartlet

For the explorer

Smartlet One - Shadow

€399,00

4.9 (14)

Stealth. Switch in seconds, leave no trace.

  • Material SS316L steel, black PVD
  • Weight ~100g
  • Compatible with Rolex, Omega, Seiko + 100 more
Buy now
Compatibility

Longines HydroConquest models supported

Covered references

29 references covered.

ReferenceMaterialDialLugSmartlet
L3.780.4.56.6Steel 32mmBlack18mmCompatible
L3.780.4.96.6Steel 32mmBlue18mmCompatible
L3.780.4.06.6Steel 32mmGreen18mmCompatible
L3.742.4.56.6Steel 36mmBlack19mmCompatible
L3.742.4.96.6Steel 36mmBlue19mmCompatible
L3.781.4.56.6Stainless Steel 41mmBlack21mmCompatible
L3.781.4.96.6Steel 41mmBlue21mmCompatible
L3.781.3.56.7Steel/Gold 41mmBlack21mmCompatible
L3.781.3.96.7Steel/Gold 41mmBlue21mmCompatible
L3.781.4.06.6Steel 41mmGreen21mmCompatible
L3.781.4.76.6Steel 41mmGrey21mmCompatible
L3.782.4.56.6Steel 43mmBlack22mmCompatible
L3.782.4.96.6Steel 43mmBlue22mmCompatible
L3.742.4.56.6Stainless Steel 41mmBlack21mmCompatible
L3.742.4.96.6Stainless Steel 41mmBlue21mmCompatible
L3.781.4.06.6Stainless Steel 41mmGreen21mmCompatible
L3.781.4.56.9Ceramic/Steel 41mmBlack21mmCompatible
L3.781.4.96.9Ceramic/Steel 41mmBlue21mmCompatible
L3.784.4.56.9Ceramic 43mmBlack22mmCompatible
L3.784.4.96.6Ceramic 43mmBlue22mmCompatible
L3.784.4.06.9Ceramic 43mmGreen22mmCompatible
L3.784.4.76.9Ceramic 43mmGrey22mmCompatible
L3.790.4.06.6Steel 41mmGreen21mmCompatible
L3.790.4.56.6Steel 41mmBlack21mmCompatible
L3.790.4.96.6Steel 41mmBlue21mmCompatible
L3.790.4.96.9Steel 41mmBlue21mmCompatible
L3.790.3.06.7Steel/Gold 41mmGreen21mmCompatible
L3.782.4.76.6Titanium 41mmGrey21mmCompatible
L3.781.4.99.6Stainless Steel 41mmBlue/Red21mmCompatible

Longines HydroConquest lug widths: 18mm / 19mm / 21mm / 22mm

The HydroConquest is Longines at its most direct. Swiss manufacture movement, 300m water resistance, ceramic bezel, and a price that remains justifiable. The L888 calibre - developed in-house at Saint-Imier - runs at 25,200 vibrations per hour with 64 hours of power reserve. The 41mm in ceramic black or blue bezel has become one of the most recommended entry-level Swiss dive watches on the market. The recommendation holds because the watch delivers. Smartlet completes it. Longines gave the HydroConquest a full next generation overhaul for 2026, with a mesh bracelet option and a frosted blue dial.
Frequently paired

Smartwatches worn with Longines HydroConquest

The most common combinations our customers wear. Find your mechanical watch and discover the right Smartlet edition.

Apple Watch
Series 0 to Ultra 3
Whoop
5.0 / MG
Garmin Forerunner
255 to 965
Samsung Galaxy Watch
Series 4 to 7
Withings ScanWatch
Light / 2 / Nova
View all brands
27 brands covered
Also compatible

Other brands

Other iconic models in the Smartlet compatibility library.

Submariner
Daytona
GMT-Master
Datejust
Yacht-Master
Sky-Dweller
Explorer
Seamaster 300m
Speedmaster
Planet Ocean
Constellation
De Ville
Monaco
Carrera
Formula 1
Aquaracer
Portugieser
Navitimer
Superocean
Avenger
Black Bay
Pelagos
Ranger
Luminor
Radiomir
Submersible
SKX
Prospex
Presage
Khaki Field
BR 03-92
Fifty Fathoms
Reverso
SUB 300
Spring Drive
Essence Leggera
Aquis
Divers Sixty-Five
Chronograph 1
Captain Cook
Superman Heritage
El Primero
Monarch
Black Bay 58 GMT
View all models
Watch brand compatibility guide

Step by step

Replace your strap
01

Replace your strap

Smartlet replaces your mechanical watch strap via the standard spring-bar system. Classic, Shadow, or Titanium. No tools required.

Connect your wearable
02

Connect your wearable

Smartlet uses a dedicated adapter or native lug pins depending on your smartwatch. The connector snaps onto the Smartlet module. Zero modification to the mechanical watch.

Wear both simultaneously
03

Wear both simultaneously

Both watches sit on the same wrist. All smartwatch sensors maintain direct skin contact and operate normally.

Questions

Frequently asked questions

  • Does Smartlet work with the Longines HydroConquest?
    Yes. The HydroConquest uses 18mm to 22mm lugs depending on case size - all natively supported by Smartlet. No adapter required.
  • Which HydroConquest references are compatible?
    All - 39mm and 41mm at 21mm, 43mm ceramic at 22mm, 36mm at 19mm, and 32mm ladies at 18mm. The full range is within Smartlet's native range.
  • Does Smartlet affect HydroConquest water resistance?
    No. Smartlet uses the spring-bar slots only. The 300m crown seals and case back are not affected.
  • Where can I buy Smartlet for the Longines HydroConquest?
    Smartlet is available at smartlet.io in Classic, Shadow, and Titanium. All finishes are compatible with HydroConquest references from 18mm to 22mm.
  • Does Smartlet damage or modify my mechanical watch?
    No. Smartlet replaces your standard watch strap using the existing spring-bar system. It makes no permanent modification to the watch case, lugs, or dial. The process is fully reversible in seconds. Your mechanical watch is unaffected and can be worn independently at any time by reinstalling its original strap. Smartlet is engineered to watchmaker tolerances and tested with the same care that goes into the watches it pairs with.