Learn
Read your reef.
Most divers read a brochure before a trip. Here is how to read the thing that actually matters once you are in the water, the reef itself, using the same 4 signals this atlas runs on.
A reef shows you its condition, if you know where to look. It is there in the coral, the water temperature, the fish, and in how long it has been since anyone last wrote it down. Learn to read those, and a single dive tells you whether a reef is holding, slipping, or already changed.
That same dive can become a record a scientist can use. You are in the water anyway, and you are already looking. The piece that is missing is knowing what you are looking at, and an easy way to pass it on. That is what this page is for.
The four signals
Learn these 4 and you can read almost any reef in the world. They are the same 4 this atlas weighs when it labels a reef, so reading them yourself is reading the reef the way the science does.
Coral cover
Reading it underwater
Look at how much of the hard bottom is still living coral, against bare rock, rubble, and algae. A healthy reef is mostly structure built by living coral, so broad fields of dead skeleton turning fuzzy green mean cover has collapsed.
What this site shows
Scuba Season shows the most recent measured hard coral cover for a location against its historical baseline, so you can see whether the reef is holding near what it once was or slipping below it.
Source: Survey networks including AIMS Long Term Monitoring and the Global Coral Reef Monitoring Network.
Heat stress
Reading it underwater
Bleaching is the reef telling you it is too hot. Coral that has gone bone white or pale and ghostly is alive but starving, having expelled the algae it lives on. Patchy white tips after a warm season are an early sign, and whole white reefs are an emergency.
What this site shows
We carry the bleaching alert level from NOAA Coral Reef Watch, updated continuously from satellite. It tells you whether the water has been hot enough, for long enough, to expect bleaching before you even get in.
Source: NOAA Coral Reef Watch, degree heating weeks accumulated over the last 12 weeks.
Fishing pressure
Reading it underwater
Count the big fish. A reef under light pressure has large groupers, snappers, sharks, and dense schools. A heavily fished reef feels empty of anything bigger than your hand, even when the coral looks fine, and missing predators is the quietest warning there is.
What this site shows
We show fishing pressure drawn from vessel activity tracked within 50 kilometres over the last year, so you know whether the fish you are not seeing were fished out rather than simply hiding.
Source: Global Fishing Watch, automatic identification system vessel tracks.
Survey freshness
Reading it underwater
This is the one you cannot see, and it is the one where you matter most. When did a scientist last look at this reef? On many sites the honest answer is years ago, or never. If the record is cold, the most useful observation of this reef might be the one you are about to make.
What this site shows
Every location carries a freshness label. Fresh means a structured survey happened within the last 2 years. Cold means no recent eyes underwater. Cold reefs are flagged as places that need fresh eyes, because they do.
Source: Survey dates from the monitoring networks above, measured against today.
Three states a reef can be in
Put the 4 signals together and a reef lands in one of 3 honest labels. These are the dots you see on the globe and the cards.
Improving
Coral cover is at or above the reef's long term baseline and steady, heat stress rarely passes a watch, and fishing pressure is light or the reef is protected. A reef close to its natural self.
Stable
Still a good dive, and the structure and the fish life mostly hold, while coral cover is moderate or slipping under warming, fishing, or both. Intact, and holding on.
Declining
Coral cover is well below baseline after one or more bleaching events, and the reef is reorganising. A dive here documents what remains, and your records here are the most valuable in the atlas.
One honest caveat: these labels rest on the signals we have, and a reef can be recovering or declining faster than our data shows. That gap is exactly why your eyes underwater matter. The method page lists every source and its limits.
The method, every dive
Read these signals once and you understand a reef. Read them the same way on every dive and you become someone who watches it. This is the routine at the heart of Read your reef, simple enough for a divemaster to teach a whole dive team in a single dive.
Before you dive
Open the reef on Scuba Season and read its state. Heat stress and freshness tell you what to expect below, and whether this is a reef whose record is cold enough that your eyes genuinely count.
As you descend
Run the 4 signals in the same order every time: how much living coral, any bleaching, the big fish, and anything that does not match what the record led you to expect. The order is the habit, and after a few dives it runs on its own.
Photograph the reef
Two photos do the work: a clear shot of any animal you can name, and a steady mapping pass over the coral. The mapping pass follows a real method, set out just below.
Back on the boat
Log it while the dive is fresh, before the next one blurs the details. Submit through Scuba Season and we route it onward, or go straight to iNaturalist. That is the whole loop, and it closes on every dive.
What to capture, and for whom
What you photograph depends on where you want the record to go. Each destination needs a different approach, and some do not need a camera at all. Here is the method for each one.
Species record
One clear, close shot of any animal you can identify. Fill the frame, get sharp focus on the subject, and include the whole animal. iNaturalist experts identify from photos on land — the photo is the record.
Any camera or phone. One shot per animal. Sharp focus on the subject.
Bleaching check
No camera. Hold the Coral Health Chart next to each coral you examine and note the lightest and darkest colour code that matches, plus the growth form. Repeat for at least 20 corals. The codes go into the CoralWatch app and become a bleaching record anyone can verify.
No camera. CoralWatch app. At least 20 corals for a valid survey.
Reef health survey
Photograph each quadrat straight down from directly above, at a consistent distance, with the frame parallel to the reef. One photo per quadrat. The photos go into MERMAID, where AI assigns benthic categories to points in the image. The diver sets up the survey on the surface; classification happens on land.
At least 12 megapixels. At least 1500 by 1500 pixels. Straight down. Consistent distance. Well lit. No motion blur. Quadrat frame required.
3D reef photogrammetry
Swim parallel passes about 1.5 metres above the reef, camera pointing straight down, one photo every 0.5 seconds. Overlap between passes lets photogrammetry software stitch a 3D surface model of the reef. Any camera with a wide lens, interval mode, and a fast memory card will work.
Wide lens. Interval at 0.5 seconds. 1.5 m above the reef. Overlapping parallel passes. Not GoPro-specific.
Structured transect
Visual census of indicator fish, invertebrates, and substrate along a belt transect. No photo required. The in-water count is the record. Requires a 3-day paid EcoDiver certification to participate in official surveys.
No camera. Slate and pencil. EcoDiver certification required.
The 3D photogrammetry method was developed by Bayley and Mogg (2020, Methods in Ecology and Evolution) and refined by the AIMS EcoRRAP program (Gordon, Figueira et al. 2023). Wildflow applies and documents this method for reef scientists.
Turn what you saw into a record
Reading a reef changes your dive. Logging it changes the science. A reef with a cold record needs one careful observer far more than a famous reef needs its thousandth photo. Here is where your observation goes.
iNaturalist
Photograph what you see. Research-grade observations flow on to GBIF, the database researchers in over 100 countries draw from.
MERMAID
Run a photo quadrat survey and your benthic data enters the platform the Global Fund for Coral Reefs uses to track reef change.
CoralWatch
Match coral colour to a simple chart and you have logged a bleaching observation anyone can verify.
Reef Check
Complete the EcoDiver course and your structured transect counts join a global reef monitoring dataset.
Just got out of the water?
Submit a sighting and we route it to the right networks for you.