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Dial&Lug
Seiko Prospex Turtle SRPE93

Turtle vs Promaster

Seiko Prospex Turtle vs Citizen Promaster Diver BN0151

The two watches everybody is told to buy first. One is a certified diver whose maker prints the overhaul price. The other runs on light and asks nothing of you for five years.

By Sawyer V. · Published

The short answer

Buy the Turtle. It is the only watch here with a diver's certification rather than a plain pressure rating, and Seiko is the only maker on this page that publishes what an overhaul costs — a flat $176 for the 4R36. It scores 8.4 against the Promaster's 6.8. Buy the BN0151 if you would rather never wind or service anything, and can accept a mineral crystal.

Disclosure · Some links below are Amazon affiliate links. If you buy through one we earn a commission at no extra cost to you. It does not decide what goes on this page or in what order — here is exactly how that works.

Top pick

Seiko Prospex Turtle SRPE93

Best for: The one to buy, and the only certified diver here

Seiko Prospex Turtle SRPE93

8.4/10

Keep Score

Seiko 4R36, 41 hours, Hardlex, 200m diver's, 45mm cushion case, 13.4mm thick, $176 published overhaul.

Seiko rates this as a diver's watch rather than merely water resistant: screw-down crown, screw case back, unidirectional bezel. That is a different standard from a pressure number on a spec sheet.

$515.00 · View on Amazon

#ad Affiliate link · Price as of October 11, 2026

Full write-up and the measured specifications are further down this page.

If you ask for a first serious dive watch you will be pointed at one of these two within about a minute. Both are 200m, both are from Japanese makers with long dive-watch records, and both have been in production long enough that the quirks are known.

They answer the question in opposite ways. The Seiko is a mechanical watch built to a dive specification and backed by a published repair price. The Citizen is a light-powered watch that asks nothing of its owner and is covered for five years.

This is the only page in this round where the winner takes full marks on our cost-to-keep line, and that is most of why it wins. Seiko is the rare maker that tells you in advance what keeping the watch will cost.

On prices: every buy button on this page reads its figure from the live price layer and stamps the date it was checked, or else reads "Check price on Amazon". No price is written into this text. Service figures quoted here are the manufacturers' own published rates.

How we picked

We have not worn these watches. What follows is what we checked instead, on documents you can open yourself — the same criteria, in the same order, on every roundup on this site. The full method is on the methodology page.

  1. 01Certification

    Seiko describes the Turtle as a diver's 200m watch — screw-down crown, screw case back, unidirectional bezel. Citizen rates the BN0151 at 200m as a pressure figure.

  2. 02Published service price

    Seiko publishes a flat $176 to overhaul a 4R caliber. Citizen publishes no service price for any watch and quotes every repair after inspection.

  3. 03Crystal

    Hardlex against mineral. Neither is sapphire; Hardlex is Seiko's hardened mineral and scores slightly higher.

  4. 04Maintenance

    A mechanical movement that wants an overhaul against a light-powered one that wants nothing at all.

  5. 05What is identical

    200m, a screw-down crown, a stainless steel case, and both on Amazon today.

Quick picks

Ranked on the Keep Score below — six published specifications, weighted identically on every page. The last row is the one we would not buy.

#WatchBest forKeep ScorePrice
1
Seiko Prospex Turtle SRPE93

Seiko Prospex Turtle SRPE93

Seiko 4R36, 41 hours, Hardlex, 200m diver's, 45mm cushion case, 13.4mm thick, $176 published overhaul.

The one to buy, and the only certified diver here8.4/10

$515.00

Check Price on Amazon
2
Citizen Promaster Diver BN0151-09L

Citizen Promaster Diver BN0151-09L

Citizen E168 Eco-Drive, mineral, 200m, 44mm, five years, 20mm lugs.

Anyone who wants a 200m watch and no maintenance at all6.8/10

$350.00

Check Price on Amazon
—
Orient Kamasu RA-AA0004E39B

Orient Kamasu RA-AA0004E39B

Sapphire, 200m, in-house hacking F6922, 41.8mm, 46.8mm lug-to-lug, 12.8mm thick, three years.

Skip this one

Neither, if sapphire is what you actually want9.0/10

$345.00

Check Price on Amazon

Prices as of October 11, 2026. Amazon pricing changes without notice — the figure on the listing is the one that counts.

Keep Score is arithmetic, not opinion — six published specifications, weighted the same way on every page. The formula is on our methodology page, so you can re-run it yourself.

01

Seiko Prospex Turtle SRPE93

Best for: The one to buy, and the only certified diver here

Seiko Prospex Turtle SRPE93

8.4/10

Keep Score

Crystal
1.3/2.5
Serviceability
2.5/2.5
Water resistance
1.5/1.5
Warranty
1.05/1.5
Strap standard
1/1
Cost-to-keep transparency
1/1
$515.00 · View on Amazon

#ad Affiliate link · Price as of October 11, 2026

Seiko rates this as a diver's watch rather than merely water resistant: screw-down crown, screw case back, unidirectional bezel. That is a different standard from a pressure number on a spec sheet.

Seiko publishes a flat $176 to overhaul the 4R36. No other maker on this page publishes anything, and it is the only product on this comparison to take full marks on our cost-to-keep line.

The 45mm figure scares people off and it should not. It is a cushion case with no protruding lugs, so the strap turns down immediately behind the case and it wears far shorter than 45mm implies.

Hardlex is the compromise. It is harder than ordinary mineral and softer than sapphire, and at this price Seiko has never moved off it.

Seiko rates this at 200m as a diver's watch, not merely water-resistant — screw-down crown, screw case back, unidirectional bezel. The 45mm figure is misleading: the cushion case has no protruding lugs.

Manufacturer specifications for the Seiko Prospex Turtle SRPE93
MovementSeiko 4R36, automatic with manual winding, 24 jewels
Power reserve41 hours
Case45mm stainless steel
Lug-to-lugNot published
Thickness13.4mm
Lug width22mm
Crystalhardlex
Water resistance200m
Warranty3 years

Specifications read from Seiko Watch Corporation product page, SRPE93.

02

Citizen Promaster Diver BN0151-09L

Best for: Anyone who wants a 200m watch and no maintenance at all

Citizen Promaster Diver BN0151-09L

6.8/10

Keep Score

Crystal
1/2.5
Serviceability
1.4/2.5
Water resistance
1.5/1.5
Warranty
1.5/1.5
Strap standard
1/1
Cost-to-keep transparency
0.4/1
$350.00 · View on Amazon

#ad Affiliate link · Price as of October 11, 2026

Light-powered means there is nothing to wind, no battery to replace and no overhaul to budget for. Over twenty years that is a real saving against a mechanical watch, and it is the honest case for this watch.

Five years of cover is the longest on this page, though it excludes the power cell, case, bracelet and strap. 20mm lugs are standard and strap choice is easy.

The mineral crystal and the missing numbers are the costs. Citizen publishes no thickness and no lug-to-lug for a 44mm watch, and quotes service only after inspection — so you cannot budget for a repair in advance the way you can with the Seiko.

Identical to the BN0150 in every specification Citizen publishes. Choose on the dial, and on nothing else.

Manufacturer specifications for the Citizen Promaster Diver BN0151-09L
MovementCitizen E168 Eco-Drive, light-powered
Power reserveNot published
Case44mm stainless steel
Lug-to-lugNot published
ThicknessNot published
Lug width20mm
Crystalmineral
Water resistance200m
Warranty5 years

Citizen's five-year limited warranty excludes the power cell, case, bracelet and strap.

Specifications read from Citizen Watch product page, BN0151-09L.

Skip this one

Orient Kamasu RA-AA0004E39B

Best for: Neither, if sapphire is what you actually want

Orient Kamasu RA-AA0004E39B

9.0/10

Keep Score

Crystal
2.5/2.5
Serviceability
2.5/2.5
Water resistance
1.5/1.5
Warranty
1.05/1.5
Strap standard
1/1
Cost-to-keep transparency
0.4/1
$345.00 · View on Amazon

#ad Affiliate link · Price as of October 11, 2026

It fails this page because it is not one of the two defaults people are pointed at, and because Orient publishes no service price.

It is here because it has the crystal neither of these has, at similar money, with a hacking in-house automatic and the smallest published dimensions of the three. It scores 9.0, the highest on this site.

If the only reason you were choosing between a Turtle and a Promaster is that somebody told you to, read our dive watches under $500 page before deciding.

On paper this is the best value in the category and it is not close: sapphire and a hacking, hand-windable in-house caliber at a price where Seiko still fits Hardlex. Orient's three-year warranty is longer than Hamilton's or Tissot's.

Manufacturer specifications for the Orient Kamasu RA-AA0004E39B
MovementOrient F6922 in-house automatic, hand-winding, hacking
Power reserve40 hours
Case41.8mm stainless steel
Lug-to-lug46.8mm
Thickness12.8mm
Lug width22mm
Crystalsapphire
Water resistance200m
Warranty3 years

Specifications read from Orient Watch USA product page, RA-AA0004E39B.

Side by side

Read from the Seiko product page for SRPE93 and the Citizen product page for BN0151-09L.
Seiko Prospex Turtle SRPE93Citizen Promaster BN0151
MovementSeiko 4R36, automatic, hacking and hand-windingCitizen E168 Eco-Drive, light-powered
Power reserve41 hoursNot published
Case45mm cushion, 13.4mm thick44mm, thickness not published
Lug-to-lugNot publishedNot published
Lug width22mm20mm
CrystalHardlexMineral
Water resistance200m diver's, screw-down crown200m, screw-down crown
Warranty3 years5 years, excludes power cell, case, bracelet, strap
Published service price$176 flat, 4R caliberNone — quoted after inspection
Keep Score8.4 / 106.8 / 10
Read from the Seiko product page for SRPE93 and the Citizen product page for BN0151-09L.

A published service price is worth more than it looks

Seiko says $176 to overhaul a 4R. That single published figure lets you calculate the real cost of owning the watch for twenty years before you spend anything, and it is the number this site exists to find.

Citizen quotes every repair after inspection, which is normal and not sinister, but it means the twenty-year figure is unknowable at the point of purchase. Our cost of ownership guide runs both arithmetics, and automatic watch servicing and costs lists every published rate by caliber.

What a diver's rating means that 200m does not

A plain 200m marking is a pressure rating. The diver's designation is a different regime: tested resistance to pressure, salt water, shock, magnetism and thermal shock, with a unidirectional bezel and a crown that locks.

For swimming and showering the distinction is academic — both watches are over-specified. For actual diving it is the whole point, and it is why the Turtle is the one we recommend to anyone who will get in the sea with it. Our are dive watches worth it page covers what certification buys.

45mm that is not 45mm

The Turtle's cushion case has no lugs sticking out of it. The strap exits immediately behind the case, so the footprint on your wrist is much shorter than the diameter suggests — which is why a watch nobody would call small is wearable on a medium wrist.

Neither maker publishes a lug-to-lug here, which is the one thing that would settle it. Dive watches for large wrists covers both, and Orient Kamasu versus the Seiko Turtle compares the cushion case to a conventional one.

Which to buy

The Turtle. A certified diver's watch on a caliber every watchmaker in America has had apart, with the overhaul price printed in advance, is exactly the thing this site was built to point at.

The Promaster is the better answer only if the appeal is a watch you never think about. If sapphire matters more than either, the Orient Kamasu has it and beats both on our scoring.

Questions people actually ask

Seiko Turtle or Citizen Promaster Diver — which should I buy?

The Turtle. It is a certified diver's watch rather than a 200m pressure rating, and Seiko publishes a flat $176 overhaul price for its 4R36 caliber where Citizen quotes repairs only after inspection. It scores 8.4 against 6.8. The Promaster is the better choice if you want a light-powered watch with nothing to maintain.

Is the 45mm Seiko Turtle too big?

Less than the number suggests. It is a cushion case with no protruding lugs, so the strap turns down immediately behind the case and it wears considerably shorter than 45mm implies. Seiko does not publish a lug-to-lug figure for it.

What does it cost to service a Seiko Turtle?

Seiko publishes a flat $176 to overhaul a 4R caliber, which is the movement in this watch. That published figure is the main reason it outscores the Citizen here.

Does the Citizen Promaster BN0151 need a battery?

No. It is a light-powered Eco-Drive, so there is no battery to replace and nothing to wind. Citizen covers it for five years, excluding the power cell, case, bracelet and strap.

Does either have a sapphire crystal?

No. The Seiko has Hardlex, its own hardened mineral, and the Citizen has ordinary mineral. For sapphire at this money the Orient Kamasu is the answer.

Sources

Every specification and figure on this page came from one of these documents. Where a manufacturer does not publish something, the page says so rather than filling the gap.

Read next

Orient Kamasu RA-AA0004E39B

Best dive watches under $500

200m, screw-down crowns and sapphire under $500. Five picks and one that isn't a diver.

Diving equipment in dark water

Citizen Promaster vs Seiko Prospex

Light-powered and five years of cover against mechanical and a published service list.

Orient Kamasu RA-AA0004E39B

Orient Kamasu vs Seiko Turtle

The better specification against the cheaper future, and the Seiko 5 that isn't a diver.

A watch movement partly disassembled on a repair bench

What a watch actually costs to keep

Published service intervals and prices, computed over 10 and 20 years. The number nobody else publishes.

Seiko Prospex SPB453J1

Are dive watches worth it?

What a diver's rating buys, who it suits, and five worth owning.