Do you try to cover as much ground as possible during a dive, perhaps in search of large marine life or a spectacular reef formation Weve all done it, and often all we have to show for our hasty quest is an encounter with the single most obvious layer of marine life.
Slow down and look a little more carefully at the creatures on and off the reef, and youll be surprised to find that all is not as it seems. Close examination reveals that many fish and invertebrates are sharing habitats and providing mutually beneficial services to make life on the reef that much easier.
The most obvious example of commensal living, one with which we are all familiar, is that of the clownfish and its host anemone.
The anemone is potentially lethal to many small fish and crustaceans, but the clownfish has come to an arrangement whereby it provides a cleaning and defence service in return for protection from predators. The constant movement of the fish through the tentacles of the anemone helps to propagate production of a mucus on the fish which protects it from the anemones sting.
But many of these commensal lives are almost secret, and to discover who is cohabiting with whom requires much closer examination - and patience. Staying with the previous example, look at the tentacles and base of the anemone (this can be quite a challenge if the clownfish is particularly protective), and you will often find that the tenants association also includes several translucent ghost shrimps, or more colourful varieties.
These are likely to be cleaner shrimps, working at keeping their host tidy and waiting for other clients to stop for a wash-and-brush-up. Try holding your hand out towards them and they will be pleased to give you a manicure!
Any reasonably sized anemone is worth checking out, whether you dive in the tropics or the UK.
The British snakelocks provides a home for small decorator and spider crabs, and in the South-west and Channel Islands you will also find shrimps living under their protection. In the Caribbean, almost every anemone has a selection of pistol or harlequin shrimps in attendance, though they dont seem interested in providing a free cleaning service.
If you dive in the Far East or Pacific, check out the carpet anemones for the very pretty porcelain crabs, which are often found in pairs. Certain species of anemone are not averse to a spot of hitch-hiking themselves, and can be found on passing hermit and decorator crabs in temperate and tropical waters, where both benefit from protection and a shared diet.
Some tenants prefer to use camouflage to mimic their chosen host, either for predatory or protective purposes. Among the most successful of these are the coral gobies which can be found on soft corals, gorgonian (fan) corals, sea whips and bubble corals.
These tiny fish (up to 20mm) match either their body hue or pattern to their host with incredible accuracy, which makes them very difficult to spot, let alone photograph.
The best method is to find yourself a potential host, such as a growth of soft coral, which offers good and comfortable access for a long wait. Get your face as close as possible and scan each branch for traces of movement. You will almost always find a coral goby if you have the patience, but not losing sight of it while you aim your camera is even more of a challenge!
Longnosed A housed camera with a macro lens is the best set-up for photographing these creatures, as it permits frame-filling images without getting too close to the subject. If you find a goby on a sea whip, dont stop looking, as you will usually discover an additional tenant in the form of a well-camouflaged shrimp. It will probably frustrate you hugely by spiralling its way merrily up and down the sea whip as you try to focus!
Choosing to study gorgonian fan corals for their tenants will inevitably lead to an encounter with perhaps the sweetest-looking fish in the sea - the longnosed hawkfish. These are far more common than many divers realise, but their pink and red chequerboard livery blends them perfectly to their host.
Once found, be patient, even if the subject appears skittish. Hawkfish generally have a patrol circuit around their host and will return to the same spot consistently to rest for a few moments. This allows you to pre-focus and concentrate on that spot for the perfect shot.
These gorgeous fish can also be found in trees of black coral, where they are easier to spot, and occasionally on pink soft corals - a lot less easy.
Once you have found a hawkfish, dont leave your gorgonian too soon. Spend a little time searching for other tenants. Ghost and decorator crabs, nudibranchs, seahorses and cowries can all be found, although their level of camouflage will vary with location.
Seahorses are irresistible subjects which you might think are easy to find because of their unusual appearance. However, their camouflage is excellent and they seem to attract heavy growths of algae, which softens their outline. They are quite common in the Caribbean, where you will often find dark-coloured examples secured by their tails at the base of the dark brown/green branching gorgonians.
There are also vivid yellow and orange examples which favour similar-coloured rope sponges as their hosts and blend with them perfectly. However, once found they make a perfect photographic subject, as they lead a very sedentary lifestyle.
It is not only sessile creatures which have these hidden tenants. Species which move slowly around the reef, such as sea cucumbers, starfish, featherstars (crinoids), sea urchins and the larger species of nudibranchs can provide a home for various other species.
Night-time is when many of the host creatures are most active. Searching the arms of featherstars will usually reveal a clingfish, squat lobster or perhaps an armoured crab enjoying a free ride. Spiny sea cucumbers are also normally host to the pretty imperial shrimps, which vary in colour from deep orange to bright pink. These are also found partnered with the exotically named Spanish dancer nudibranch, nestled among the flamboyant gills of the animal.
In Far Eastern waters particularly, almost every invertebrate is worth a good scan, as you will find needle and imperial shrimps with sea urchins, spindle cowries and mimic nudibranchs on sea fans, and even miniature hermit crabs clinging to the backs of spiny starfish.
Perhaps the most exotic and attractive mimic is the ghost pipefish. These are supposedly quite common in the Far East, but are perfectly equipped to secrete themselves among featherstars and soft corals.
When you do find one of these hidden creatures the satisfaction is immense, and the next discovery is that much easier, as your eyes are tuned into the macro environment to spot the tell-tale signs. So when you have dived all the big sites, or find yourself returning to familiar locations, drop into a lower gear and aim to cover perhaps just a few metres during your dive. However, be aware of your movements close to the reef - good buoyancy control and tidy and secured gauges and hoses will ensure that you do not damage the delicate environment.