Which is cheaper, the Formex Reef 42 mm or the Seiko Prospex Sea?

At MSRP the Seiko Prospex Sea is the cheaper of the two at $1,500, against $2,414 for the Formex Reef 42 mm — a $914 gap before any retailer discounting.

Which is bigger, the Formex Reef 42 mm or the Seiko Prospex Sea?

The Seiko Prospex Sea wears larger at 43.5mm versus 42mm for the Formex Reef 42 mm — a 1.5mm difference across the dial.

Which has better water resistance, the Formex Reef 42 mm or the Seiko Prospex Sea?

The Formex Reef 42 mm is rated to 300m versus 200m for the Seiko Prospex Sea.

Which has a longer power reserve, the Formex Reef 42 mm or the Seiko Prospex Sea?

The Seiko Prospex Sea carries a 70-hour power reserve against 56 hours on the Formex Reef 42 mm.

What movement does the Formex Reef 42 mm run compared to the Seiko Prospex Sea?

Both watches run automatic movements — the Formex Reef 42 mm uses the Sellita SW300-1 and the Seiko Prospex Sea uses the 6R35.

Side by side

Formex Reef 42 mmvsSeiko Prospex Sea

The numbers, the dial colors, the calibers — laid out so you can stop flipping between tabs.

Formex Reef 42 mm

reef-42mm-automatic-cosc-300m-black

MSRP $2,414

Seiko Prospex Sea

spb349j1

MSRP $1,500

At a glance

11 of 29 specs differ

Diameter

Reef 42 mm42mm

Prospex Sea43.5mm

Power Reserve

Reef 42 mm56h

Prospex Sea70h

Water Resistance

Reef 42 mm300m

Prospex Sea200m

MSRP

Reef 42 mm$2,414

Prospex Sea$1,500

Full specifications

Case

5 specs

Diameter

42mm

43.5mm

Thickness

11.4mm

13.3mm

Lug-to-Lug

47mm

51mm

Material

Stainless Steel

Titanium

Water Resistance

300m

200m

Crystal & Dial

2 specs

AR Coating

Inner

Anti-reflective coating on inner surface

Lume

Super-LumiNova

LumiBrite on hands and index(es)

Movement

3 specs

Caliber

Sellita SW300-1

6R35

Power Reserve

56h

70h

Jewels

Pricing

1 specs

MSRP

$2,414

$1,500

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What people say

Owners + reviewers, side by side

Synthesized for each watch independently from owner discussions, enthusiast forums, written reviews, and video reviewers.

Formex Reef 42 mm

The Formex Reef 42 mm is widely praised for its comfortable bracelet featuring a micro-adjust clasp, COSC-certified Sellita movement, and excellent build quality. Owners appreciate the gradient dial's visual appeal and the overall wearability. Some owners note the seconds hand does not perfectly align with markers, and one owner found the lugs' taper hinders third-party strap fit. The bracelet's length and sporty design are noted as limiting versatility by some. On balance, owners and reviewers rate the Formex Reef 42 mm highly for its impressive wearability and value at the price point.

Seiko Prospex Sea owners and reviewers praise its Marinemaster-style aesthetic, excellent case finishing, and impressive LumiBrite lume. The watch is powered by the 6R15 movement with a 50-hour power reserve and comes with both a steel bracelet and a silicone strap. Some owners find the Seiko Prospex Sea to be a great value and a suitable first "proper" watch, while others report it is uncomfortably big, thick, and heavy on smaller wrists. Reviewers note the GMT function is secondary with a less prominent scale, and the bezel's quieter clicks may not appeal to all. On balance, owners and reviewers rate the Seiko Prospex Sea highly for its classic design and finishing at its price point.

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