The Héron Marinor Rainbow is the Ultimate Value Proposition Decompression Timer

Confession time, I like decompression timer watches. They’re a fun niche within what is already one of the most prominent watchmaking niches, dive watches. If you’ve not come across one before, they’re a style of dive watch that features a circular table in the centre of the dial that displays information related to how long you have to spend on decompression stops when resurfacing from a dive in order to prevent the bends. Microbrand Héron have released their interpretation of this archetype with the launch of the new Héron Marinor Rainbow.

Straight away the thing that sticks out to me is the value. This is the first decompression timer I’ve seen in the past five years or so with a sub-£1,000 price tag. The Mido Ocean Star Decompression Timer 1961, Delma Retro Shell Star and Christopher Ward C65 Super Compressor Elite are all in the £1,000 – £1,500 bracket while the Marinor Rainbow is £510 on steel bracelet and £460 on rubber strap. You might expect then that it’s got less impressive specs but that’s not the case.

Said case measures a well-proportioned 39mm x 12.9mm (including crystal) in stainless steel with a 300m water resistance rating. This is a better water resistance rating than both the Mido and Christopher Ward, meaning the Marinor Rainbow actually outperforms the pricier pieces. I also personally think that it’s got a much cleaner and more legible display than its rivals as well.

In the centre is a 12-hour display (my one irk being that the hour hand extends past it instead of pointing to it), around which is the rainbow decompression timer. Decompression timers are difficult to get right because they have to display a lot of information in a relatively small area meaning they can look cluttered and difficult to read. The Marinor Rainbow avoids this by employing a bold, graphic style.

Wherever a number is noted, there’s a black gap in the recessed, sandwich rainbow scale providing strong contrast to the white numerals, ensuring they’re legible. The black areas also provide a clear visual break where there’s a change in decompression timing required. Héron actively acknowledge they were inspired by heritage models from brands like Mido, so they’ve evidently studied and made their own improvements. That all said, I should probably explain how the scale works.

The numbers on the bridge at 12 o’clock denote the depth at which you are swimming in metres. You then follow the relevant scale clockwise for the amount of time in minutes you spend at that depth. Where you intersect with a number on the scale, that number denotes how much time you need to spend on decompression stops when resurfacing. You’ll note that the first numeral on each of the scales is a 0, meaning that if you spend less than that amount of time at that depth, a decompression stop is not required.

Outside the decompression timer is a 60-minute scale and beyond that we get to the unidirectional bezel with 60-minute timer. You can use the bezel in conjunction with the decompression table to stay safe while diving. When you’re starting your stop, rotate the bezel so that the arrow lines up with the minute hand to mark its starting point and track elapsed time easily regardless of what the local time is.

Beneath the rainbow dial is housed the Miyota 9039 automatic movement with 42-hour power reserve. This is the area where the Marinor Rainbow is maybe a bit behind its rival decompression timers because Christopher Ward uses a COSC movement and the Mido has an 80-hour power reserve. However, I think the Miyota movement is perfectly acceptable given the price of the watch, which to reiterate is about half that of the rivals we’ve been comparing it to. Need I say impulse buy?

More details at Héron.