Which Longines HydroConquest to buy: 39mm, 41mm or 42mm, automatic, quartz or GMT (2026)

For most people, the best HydroConquest is the newer 39mm automatic: it has a ceramic bezel, a silicon balance spring and a 72-hour power reserve, according to Longines. For bigger wrists, the 42mm is the same watch. For less money, the 41mm automatic has the same calibre and power reserve.

Every watch here is sold new by Goldsmiths, a UK authorised Longines retailer. Prices are Goldsmiths' own on the date shown.

How we chose

We went through every HydroConquest Goldsmiths has in stock and read Longines' own product pages for the calibre, thickness and lug width of each version. That's how we found the differences that aren't obvious from the name, including that three of the watches Goldsmiths lists simply as "HydroConquest" are in fact the HydroConquest GMT, according to Longines. We earn a commission if you buy through our links, which never changes the price you pay. For the rest of Longines' range, see our best Longines watches.

Every HydroConquest, compared

Calibres, thicknesses and lug widths are from Longines' website; prices are Goldsmiths' for the version shown. Every HydroConquest is water resistant to 300 metres.

Which size: 39mm, 41mm or 42mm?

• 39mm suits most wrists, and it's the size we'd choose. It's the newer generation, and its 20mm lug width means plenty of straps fit if you want a change from the bracelet.
• 42mm is the same newer watch for bigger wrists, and Longines gives it the same 11.7mm thickness as the 39mm, so it isn't chunkier, just wider.
• 41mm is the earlier design. It's the least expensive automatic HydroConquest, and Longines gives the same L888.5 calibre and 72-hour power reserve as the newer watches.

The best HydroConquest overall: the newer 39mm

Longines' page describes a self-winding movement with a monocrystalline silicon balance spring and a power reserve of up to 72 hours, a stainless steel case with a ceramic bezel, and a bracelet with a folding clasp and a micro-adjustment system for fine-tuning the fit. It's 11.7mm thick, according to Longines.

Best HydroConquest overallLongines HydroConquest L37794966 · 39mm · Automatic · 300 m water resistant £1,925Price at Goldsmiths, 28 October 2026 Full specsSee it at Goldsmiths

The same watch comes with a green or black dial, and the 42mm in the same colours.

Longines HydroConquest 35 watches at Goldsmiths, £1,300 to £2,650. Shop the HydroConquest

The best value automatic: 41mm

If you want a Swiss automatic dive watch from Longines and every pound counts, this is it. Longines gives it the same L888.5 calibre and power reserve of up to 72 hours as the newer models, with a screw-in crown and a unidirectional rotating bezel. It's slightly thicker, at 11.9mm, and Goldsmiths lists the same five-year guarantee.

Best value automaticLongines HydroConquest L37424966 · 41mm · Automatic · 300 m water resistant £1,300Price at Goldsmiths, 28 October 2026 Full specsSee it at Goldsmiths

At the time we checked, it cost about the same as the 42mm quartz: £1,300 against £1,350. For most people, that makes the automatic the better buy.

The best for bigger wrists: the newer 42mm

The same newer generation as the 39mm, at the same 11.7mm thickness, with a 21mm lug width according to Longines.

Best for bigger wristsLongines HydroConquest L37884966 · 42mm · Automatic · 300 m water resistant £1,925Price at Goldsmiths, 28 October 2026 Full specsSee it at Goldsmiths

The best HydroConquest GMT

A GMT shows a second time zone on a separate hand, which is useful if you travel or work with people abroad. The HydroConquest GMT uses Longines' L844.5 calibre with a power reserve of up to 72 hours, according to Longines, in a 41mm case that's 12.9mm thick.

Best GMTLongines HydroConquest GMT L37904566 · 41mm · Automatic · 300 m water resistant £2,650Price at Goldsmiths, 28 October 2026 Full specsSee it at Goldsmiths

Goldsmiths also sells it with green and blue dials, listed as "HydroConquest"; Longines' pages show they're the GMT, with the same L844.5 calibre.

For more travel watches, see our best GMT watches.

The best quartz HydroConquest

A 42mm quartz with the L157.3 calibre and a thickness of 11.3mm, according to Longines: the thinnest men's HydroConquest, and one you never need to wind.

Best quartzLongines HydroConquest Quartz L37694966 · 42mm · Quartz · 300 m water resistant £1,350Price at Goldsmiths, 28 October 2026 Full specsSee it at Goldsmiths

The best HydroConquest for women

The 30mm quartz HydroConquest is a proper small diver: 9.55mm thick with a 16mm lug width, according to Longines, water resistant to 300 metres and with a unidirectional rotating bezel.

Best for womenLongines Hydroconquest L33694096 · 30mm · Quartz · 300 m water resistant £1,300Price at Goldsmiths, 28 October 2026 Full specsSee it at Goldsmiths

The 32mm version has a ceramic bezel, in steel or with gold-coloured PVD, according to Goldsmiths.

Special editions

Goldsmiths also has the 2026 Commonwealth Games limited edition in 39mm and 42mm, with a turquoise dial and a rubber strap.

HydroConquest or something else?

A step up in price, the TAG Heuer Aquaracer is the main rival, with solar, automatic and GMT versions: see which TAG Heuer Aquaracer to buy. Under £1,000, the Tissot Seastar gives you a Swiss automatic diver for much less: see our best dive watches under £1,000. And if the budget goes much higher, the Omega Seamaster Diver 300M is the classic: see which Omega Seamaster to buy.