SeaLife ReefMaster RM-4K review: capture an underwater world

Can this waterproofed compact camera that shoots 14MP stills and 4K video let you create your own version of Attenborough’s Blue Planet?

SeaLife ReefMaster RM-4K camera on a log in front of a river
(Image: © Gavin Stoker / Digital Camera World)

Digital Camera World Verdict

Compact palm-sized camera and underwater housing combo that at just 202g won’t weigh you down. Yes, it might seem I'm being asked to pay through the nose for what resembles a matchbox-sized point-and-shoot plus a plastic-y case. But the premium price is partly justified by the device letting me capture 14MP pictures and 4K video at deeper-than-usual 40-metre depth. Arguably, in allowing me to create imagery in conditions I wouldn’t otherwise be able to, it’s actually priceless. Just be sure the housing is screwed on super tight before venturing into any water.


  • +

    14 megapixel stills and 4K-resolution video

  • +

    Records to removable microSD card

  • +

    Can withstand watery depths of up to 40 metres

  • +

    Lightweight and miniature set up at just 202g


  • -

    Plastic-y build yet premium price point

  • -

    Small, low-res LCD makes it difficult to determine detail

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    microSD card is an essential extra

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    Potential for user error and leaks if the housing is not fastened securely enough via the provided plastic cog

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These days I don’t always need bulky and expensive camera housing to be able to shoot more than passable quality stills and video underwater. In the last ten to 15 years there’s been a handful of rugged consumer-targeted compact digital cameras that can be used for going snorkeling with. These can then be run under the tap to clean if they get covered in sand or grit. I just need to make sure the rubber-sealed latch prevents water ingress to the memory card and the battery compartment is clamped tightly shut before entering the sea or swimming pool.

Unlike such standalone examples, however, the SeaLife ReefMaster RM-4K comprises two components. Yes, it’s a compact camera – very compact in fact, as the camera component is no bigger than a matchbox and fits snugly in the palm of my hand. But the camera needs to be secured within an external plastic housing, here simply fastened into place and made watertight via a hand-turned chunky plastic cog. The rear of the housing is translucent, so I can view the camera’s back screen to aid composition, while there’s a clear circular window provided for the lens at the front. Fittingly enough, given the camera’s intended use, this 14mm equivalent lens gives us a wide-angle ‘fisheye’ lens, the effect getting noticeably more pronounced the closer I'm shooting to a subject.

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Sensor14-megapixel CMOS sensor
Sensitivity rangeISO100 to ISO3200
Video4K maximum resolution at 30fps, or HD video at 60fps
Lens14mm equivalent in 35mm terms
Monitor2-inch, fixed 230K-dot resolution LCD
Battery lifeTwo hours of video or 500+ images
Dimensions4.9 x 10.5 x 2.6 cm / 1.9 x 4.1 x 2.6 in (underwater housing) 3.3 x 5.8 x 4.1 cm / 1.3 x 2.3 x 1.6 in (camera alone)
Weight202 g / 0.45 lbs

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Gavin Stoker

Gavin has over 30 years’ experience of writing about photography and television. He is currently the editor of British Photographic Industry News, and previously served as editor of Which Digital Camera and deputy editor of Total Digital Photography

He has also written for a wide range of publications including T3, BBC Focus, Empire, NME, Radio Times, MacWorld, Computer Active, What Digital Camera and the Rough Guide books.

With his wealth of knowledge, Gavin is well placed to recognize great camera deals and recommend the best products in Digital Camera World’s buying guides. He also writes on a number of specialist subjects including binoculars and monoculars, spotting scopes, microscopes, trail cameras, action cameras, body cameras, filters and cameras straps.