Coral-Sensitive: Learn about CORAL!

Coral Sensitive
Coral Sensitive

Marine LifeCoral-Sensitive

RICHARD ASPINALL looks at how to make your reef-dives even better; for you and the coral.

ALL DIVERS REMEMBER their first coral-reef dive experience. For me, it was on the generally unexciting site of Ras Katy, an easy check-dive location for boats leaving Na’ama Bay on the northern Red Sea liveaboard circuit.

I had recently qualified as an Open Water Diver in a cold quarry in autumn, and here I was seeing brightly coloured tropical fish swimming around real coral bommies! I’ll never forget that experience.
We all know that coral reefs are threatened and that we should be concerned for their well-being, but I want to offer some suggestions as to how we can best enjoy these remarkable habitats.


I’m going to make quite a few generalisations here that may well have biologists screaming, but here goes.

The basic building block of a coral reef is the coral polyp. Each polyp contains a mouth surrounded by a ring of tentacles often containing nematocysts (stinging cells), a digestive system and not a great deal else. Imagine a small anemone and you’re warm.

Some corals are single polyps, such as the cup corals found around UK coasts or the disc-like mushroom corals of the tropics, but most are colonial and arise from asexual division of other polyps as the colony grows.

Some of the colonies we call coral are not actually coral at all. Fire coral, for example, is a type of hydrozoan. But generally we have two categories: hard coral and soft coral.

Biologically, corals are found within the class Anthozoa (literally “flower animal“). Within this are groups of more closely related animals such as the Octocorallia, named for their eight tentacles per polyp.

Next time you’re enjoying Dendronepthya soft corals at Ras Mohammed, you can give them their posh name but waste no time trying to count their tentacles, or you’ll miss the shoals of big stuff and strain your eyes.

The stony corals are in the Hexacorallia sub-class (multiples of six tentacles), and most of what we consider “proper” corals are in the order Scleractinia. These are the stony corals that form reefs, or get in the way of the wreck, depending on your point of view. And there are many more sub-categories that are constantly being revised.

Corals lay down calcium to form the reef, and in essence, as they metabolise, they alter the pH level inside their skeletons.

This causes dissolved substances in sea water (mainly calcium) to form tiny crystals that build up in layers at the polyp’s base. Each coral species does this slightly differently, hence the unique shapes.

Because this process depends on light, scientists can analyse coral skeletons from the past to estimate growth rates and learn about previous climate patterns. This is a finely balanced process, and as the seas become more acidic, corals will suffer.


The check-dives I mentioned have several functions. They tell divers and guides that their kit is working, but also make sure we get our buoyancy right.

I’m still surprised that so many people dive overweighted, and find it hard to control their buoyancy over all those fragile and often very old coral growths they’ve paid so much to enjoy.

Remember also to adopt a good body position, and consider using trim weights if necessary. This will protect the reef but also make you more streamlined,with all the benefits that offers: lower gas consumption, longer dive time and less strain on your legs.

We’ve all at some time in our diving careers felt we needed extra weight to get down, and stay down, but if you now feel you need to work on your buoyancy and trim, take extra care over the coral and work with your dive-guide.

As you relax and gain confidence, it will get easier.

And dive-guides are there to assist – I’ve yet to meet one who wouldn’t rather help you get your buoyancy and trim correct than see you plough into corals or kick up silt in a wreck.

Make sure to secure those regs, dangling cameras, reels and SMBs, too. I’ve often seen huge reel/SMB combos on long lanyards dragged across coral by divers who are finning well above it.

Make sure that you have your clips and lanyards rigged correctly before you leave home.

Fins can be a problem too. There is nothing more sickening than feeling through your fins the scraping and snapping as a cloud of delicate coral life tumbles to the seabed. You may well get a telling-off from the guide and feel awful for the rest of the dive.

Adopting a horizontal position and being properly trimmed will help to stop you kicking downwards, and we should all take real care in swim-throughs, overhead environments, wrecks and when negotiating complicated reefs made of bommies and channels with limited turning-space.

Try to build a mental image of yourself that includes your fins.

Try using a different type of fin-kick when around corals and delicate life. Flutter-kicks can be usefully small but my preferred kick, which does take some time to master, is the frog-kick, with knees bent and fins above the plane of the body, allowing forward propulsion and a good degree of control.


The diversity of life on coral reefs far exceeds that found in all other marine habitats, but much of it is quite small and really good at hiding and, like me, you may be contemplating adding stick-on lenses to your mask to help those tired eyes.

Taken in slowly, coral reefs reveal a level of intricacy that we often miss. The closest many of us come to fully appreciating all the little stuff is perhaps during a night-dive, when our awareness is reduced to the world visible in our torch-beam.

You’re rarely missing out if you travel no more than 50m from your entry-point. Try to look more closely at the coral heads and find the tiny, delicate fish that swim among the branches, or the crabs that spend their lives in aptly named corals such as the bird’s nest or cauliflower. You’ll see them waving their pincers at you, performing their role of protecting the coral and getting a secure home as their reward.

Speeding over the reef you’re likely to see less, though it might take a few dozen dives to realise this.

Discuss it with your buddy beforehand, and try a dive on which you find a few bommies and spend time watching the comings and goings there.

Find a cleaning station perhaps, or watch anemonefish in their hosts. Diving is only a race when you’re in a drysuit and desperate to wee.


As someone aspiring to be a good photographer, my camera comes with me on just about every dive, but on that rare occasion when I haven’t charged a battery and it stays on the boat, I have to admit that the diving experience is more satisfying.

Obviously it’s better not to suffer the pain of missing out on a shot of a passing manta, so we’re talking about a balancing act here. We all want great pictures, and photography can help you learn about your subjects’ behaviour and allow you to identify animals after the dive. Yet a rest is as good as a break.

Your long-suffering buddy, tired of being your unpaid model and chief critter-spotter, might welcome a little more of your attention, too.


Many corals don’t need light to survive and don’t contain symbiotic algae. These are called “azooxanthellate” corals, though you may want to practise before dropping this word into a conversation.

Usually deepwater corals, they survive by absorbing nutrients from the water or catching prey in the zooplankton. Some species with large polyps can even catch small fish and invertebrates.

In general, however, most require light. That’s why I believe that the shallows hold the best a reef can offer. If you want high-energy diving, go where the energy is greatest!

If you usually spend your time in the 20-30m range looking for morays you’re missing a world of tremendous colours, shoals of fish grazing on algae and potentially longer and safer dives.

If you’ve clocked up some depth on recent dives, a long gentle bimble at 10m is a good idea physiologically as well.

Just warn dive-guides if you intend to do this. Their dive-plans will rarely include completing the full dive in the sub-10m zone. It’s also worth staying well away from the reef in anything but the calmest conditions.

In areas of surge the life is fascinating, but it’s easy to be swept into, even onto, the top of the reef. Perhaps stay around 12m unless you can see that there’s no risk of damaging the coral or yourself.

All those colours, by the way, are pigments that the corals produce to protect themselves and the algae living in their tissues from the harsh sunlight in the tropics – especially light in the UV part of the spectrum.


We divers are aware that we should all use fewer resources and try harder to limit our ecological impact, but there some very simple things we can do to make an immediate difference.

In the UK we have good recycling facilities, but many dive destinations don’t even have proper waste-disposal, let alone anything close to recycling. I’ve been to many idyllic destinations where, hidden from the guests, all the rubbish is burnt or dumped in the desert, ready to be blown out to sea.

So take less stuff with you, leave unnecessary packaging at home, reuse plastic bottles and take spent batteries home.

And if you chuck a cigarette-end overboard expect a telling-off, if I’m on the boat.

You might try to minimise your chemical impact on reefs. Certain chemicals such as oxybenzones, as used in sun-screens, are harmful to corals, and are washed onto reefs by snorkellers and divers, concentrating the chemicals around tourist hotspots.

The global impact of such products is debatable, but remember that many dive-boats empty their waste-tanks at sea. Avoid products that contain plastic microbeads as well. Production and import of cosmetics using these beads has been banned in several countries (including in the UK from 2017), but there are still huge amounts of these pesky plastics out there.

You might also want to get involved in supporting or actively taking part in research and conservation programs.

Dive shows are a great way to not only donate or buy a T-shirt but to find out more about conservation projects that offer some great diving.


A Red Sea dive might feature astounding growths of Acropora humilis or Stylophora pistillata, but it takes a real expert to know if it was really Acropora hemprichii and Stylophora subseriata.

Scientific names aren’t easy to remember. Over the years people have come up with names to describe coral groups based on their shape and growth pattern: staghorn corals, plate corals, finger corals, brain corals, leaf corals and so on, making them easy to learn.

Biologically these names don’t always hold water, but by recognising that there are different corals on a reef and that different types of corals are found in different locations and conditions, we build a picture of reefs as dynamic places.

Corals compete with each other for light and space and are, however slowly, jostling each other for position. Reefs are violent places full of mini turf wars. A reef with fewer types of corals may be suffering from diver pressure, overfishing, run-off from nearby land or pollution.

Once you can identify one set of corals from another, you start to notice the smaller differences.

Admittedly this can be a life-long challenge, as there are roughly 300 species of reef-building corals in the Red Sea alone, and the numbers change regularly as researchers find out more and revise their classifications.

As with all things in life, the more you learn about a subject, the more you appreciate it. Divers have a direct interest in coral reefs and the species that live on and in them, so let’s not take coral for granted.


The UK is not blessed with many coral species but we do have a few of note. Should you be diving amid the polystyrene-like lumps of dead men’s fingers, you’ll be looking at a genuine soft coral, closely related to tropical leather corals.

Reef-building corals are a little harder to find and are represented in UK waters by a few species of cup coral, small anemone-like animals that look attractive, especially the rare sunset cup coral. Most cup-coral species are found in the warmer waters around the South-west, but the Devonshire cup coral, despite its name, is found on many UK coasts.



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