A GOOD RULE OF THUMB when looking for prolific marine life is to go where the currents are. The Straits of Gibraltar certainly qualify on that score. At Los Bolos (because you need the balls to dive it) the current slackens off a bit at high water, and I haul my way down the anchorline to gain a little shelter from the reef.
     Canyons and crevasses separate huge blocks of rock standing 10m high from the 32m seabed. Broad splurges of purple, yellow and orange are gorgonians, gorgonians and cup corals respectively.
     My buddy for the day is Peter Deth, owner of Happy Divers, further up the coast in Marbella. A few nights ago I had been enjoying a beer with Peter and Manolo, owner of Gibsub Diving in La Linea. Manolo was describing the dive at Los Bolos and Peter had commented: If it is exciting and dangerous, I want to do it.
     Well, at slack(ish) water and for an experienced diver it isnt really dangerous, but it certainly is spectacular and exciting. Nevertheless, I cant help thinking that here I am in the Straits of Gibraltar, hiding in crevasses and below overhangs from swirling unstable currents, and I am diving with Deth. Maybe its just the narcosis.
     While there is plenty of nice diving along the Mediterranean coast, La Linea and the Straits of Gibraltar are where divers in the know head for an adrenaline fix. Using the autopista running just inland, the journey is practical as a day trip from anywhere along the Costa del Sol.
     Manolo had collected me from Marbella and the journey took about an hour. A couple of Peters divemasters from Happy Divers have joined us on their day off, as has an instructor from Diving Marbella. The boatload is completed by Sebastian, co-owner of Gibsub Diving and one of its regular divers from La Linea.
     A group of three more divers from Cadiz had planned to join us, but in the end couldnt make it. It works out nicely. With three fewer divers, there is room in the RIB for a second tank each, so we dont have to return to shore before hauling our way down the anchorline again at Cantil de las Gorgonias.
     Here, the scenery is less severe; a huge domed reef with ledges and ridges running across the current. The overall impression is one of yellow, from the carpets of yellow gorgonians that dominate the sessile marine life.

Free tow
Now, a couple of hours after high water, the current is stronger and more focused. Billions of gallons of water have passed their moment of indecisiveness and agreed to continue going in the same direction, into the Mediterranean, as surface water usually does in the Straits.
     Once in the Mediterranean, surface water evaporates, salinity increases, density increases, the water sinks and, 100 or so metres down, the Straits flow the other way.
     It is rumoured that the Phoenicians used sea anchors on long lines to get a free tow out of the Mediterranean from the deep current. Then, in the past century, submarines used the deep and shallow currents to run the Straits quietly, with minimal motor power.
     Just along the ridge from where the anchor is firmly hooked on by a single prong, I find a window in the reef lined with orange cup corals, a concentrated jet of water ripping through and out the other side.
     It looks just about big enough to fit through, but to do so would have scoured its beauty. I am also aware of a word of caution from Sebastian, to beware of getting wedged by the current in narrowing swim-throughs.
     He had actually been aiming to drop the anchor further along this reef at La Cueva del Cantil, but on the way down the current had got the better of the anchor and shifted us a couple of hundred metres eastwards.

Free tow
Behind the next ridge, I find an octopus walking the reef. At first it is cautious but then, while I hold off, it becomes curious and reaches a tentacle towards me. We briefly touch fingers before settling down next to each other in a back eddy.
     While reefs further into the Straits are dive sites for more experienced divers, closer to the coast are plenty of sites that most divers can enjoy. I join a regular Friday outing with an average mix of tourist divers from Marbella, journeying to La Linea by minibus and then on to the RIB, out across the bay of Algeciras past anchored fleets of merchant ships, and east along the Straits.
     Sebastian hooks the anchor on to La Piedra de las Corvinas (the Rock of the Drums), a plug of rock some 50m across, rising 12m from a 30m seabed and cleft through the middle along the current.
     There is still a current, but at least everyone can swim against it on the bottom, and the site is sufficiently small that the group of divers cant become too dispersed.
     Its an orange dive. While there are still plenty of yellow and purple gorgonians, the predominant marine organisms are orange cup corals and clouds of orange anthias. A no-stop dive on 32% nitrox is just about right to make a slow circuit of the rock, followed by a quick return to the leading edge and a drift with the current through the cleft that splits it in two.
     Most divers have elected to return to ascend the anchorline. Those unfamiliar with getting into a RIB in a current are coaxed through the process of removing kit in the water while keeping hold of the boat. Sebastian then unclips the RIB from the anchor buoy to recover a pair who have surfaced on a delayed SMB, an essential piece of safety kit for these waters.
     Again with two cylinders each in the RIB, we head inshore to a wreck that is dead easy to find, El Barco de las Habichuelas. Its goalpost masts still stand above the water.
     It must be something about the cultural background of divers in Spain; wrecks are nearly always described rather blandly by their cargo or location. El Barco de las Habichuelas sounds inspiring until it is translated to the rather bland Green Bean Boat.
     Despite the uninspiring translation, this is quite a nice wreck, with a partly intact stern canted to starboard, the bow intact and on its port side, and everything else flattened.
     A couple of divers on an open-water course had obviously missed the first dive and do two lessons on the wreck, the rest of us making our second dive in between. With the seabed inshore of the stern at only 6m, it is an ideal training location, though I suspect that when they finish the course and get back to more typical easy dive sites, they will find that they have been spoiled.
     I am straight inside the stern and the steering compartment, then along a passageway with cylinders of gas below and steps above leading to the surface, where the superstructure has broken away. Back outside, the top of the diesel engine is just visible from among the tangle of debris collapsed into the engine-room.
     There are plenty of good and cheap places to eat in La Linea, but the minibus and divers have to get back, and sadly we stop off for the slowest fast food ever under the golden arches. After 35 minutes, we conclude that one of the slow and casual restaurants would have been a faster and more pleasant choice.
     A day later and I am back again. Just round the corner from the Green Bean Boat, I dive an altogether different kind of wreck site, ancient Roman and Phoenician remains where ships used to anchor while waiting for good weather before passing through the Strait.
     Shards of amphorae and stone anchors are just a small aspect of a dive site that has all the colour I have come to expect from the area.
     With a medium zoom lens on my camera, I swap from the amphorae to looking for smaller life between the forests of fans. When I start to look closely, I have no trouble finding plenty of blennies, gobies and nudibranchs to keep myself busy.
     Later, at the Green Bean Boat again, I follow Sebastians tip that many of the regular photographers venture well off the wreck onto the surrounding rocks. Taking care about navigation and straying into the current, I am rewarded with everything from moray eels to octopuses, plus a shoal of thousands of silvery fish that I couldnt identify at the time. I have been told since by an angler that they may have been blue whiting.

Yellow gorgonians at Cantil de las Gorgonias
Sebastian tidies the rope after anchoring just off the stern of the Green Bean Boat
Female rainbow wrasse
Stairway inside the remains of the superstructure. Orange cup corals line the interior walls
Photographing a purple gorgonian
A goby makes its home among the broken remains of amphorae
Orange cup corals


GETTING THERE: Iberia flies daily from Heathrow to Malaga. La Linea is an easy drive from most of the Costa del Sol.
DIVING: The dive centre is now run by Diving Costa Del Sol, which offers nitrox and full rental equipment, www.divingcostadelsol.com. Also visit www.gibsubdiving.net for diving information.
ACCOMMODATION: Many mainstream holiday companies provide packages inclusive of hotel and charter flights.
WHEN TO GO: Diving is available year round, but is more likely to be restricted by weather outside the summer season. Local divers tend to wear 7mm one-piece wetsuits.
COSTS: Return flights from Heathrow to Malaga cost from£134 return. Accommodation costs vary upwards from a couple of hundred pounds for last-minute out-of-season week-long deals. Diving Costa Del Sol charges 29 euros per dive with tanks and weights, multiple dives discounted.
FURTHER INFORMATION: Spanish Tourist Office, 020 7486 8077, www.tourspain.co.uk or www.spain.info.