Situated towards the west of Galway Bay, between the famous limestone of the Burren and the harsher peaty landscapes of Connemara, the Aran Islands are built from limestone and it is largely this which is responsible for much of their spectacular diving; for, as it weathers and erodes, it forms indented cliffs, caves, cracks and fissures, which underwater form dramatic walls, huge gullies, massive boulders and some really weird rocky formations.

Less well documented than Ireland's beautiful scenery and her reputation for hospitality, is the rather changeable weather. Photographers revel in the ever-changing light, the dark skies and the crisp, clear air; but for divers they mean that alternative sites are always a requirement. So, sometimes you have to forego diving in the Arans if the weather really is impossible. And, forget the Arans if you want to dive wrecks (one does sit high and dry on Inish Oirr, though). But if you're attracted by scenery and marine wildlife, you'll be forever beguiled.

Your first step is probably to seek out Nick Pfeiffer. For the past two years Nick, 29, has run Galway Bay Scubadivers and has that most essential of all requirements - local knowledge. He also has extensive experience of the dive sites he uses, many of which were unknown until found and explored by Nick and his friends. He also, handily, has a degree in Fisheries Science and extensive experience in the marine environment, having managed a salmon farm, been involved in research work in the US, and worked for the Department of the Marine (Ireland's equivalent of the Ministry of Agriculture, Fisheries and Food).

His operation is unusual in that he currently operates using a 6.5m Humber RIB, with a potent 150hp outboard, from the mainland. It only holds eight divers and he's hoping to get a bigger boat. On the minus side, there is at least a half hour trip to the Arans every day (and it can be a very rough, hard ride, although Nick does run the boat carefully and with some passenger comfort in mind!). There is the advantage, however, that should the weather turn and prevent island diving, the sheltered creeks, bays and inlets of the mainland Connemara coast can be explored. Nick also uses these for some spectacular night dives.

We were a group of eight when we dived with Nick in June, all involved in some kind of marine biology work and with considerable knowledge of the undersea environments found around Britain and Ireland. We chose the Arans because the marine life was rumoured to be good. And to say that none of us were disappointed would be an understatement! Our first few dives on the islands were on rocky walls with overhangs and deep horizontal fissures where softer rock had been eroded from the geological layering. They were simply stuffed with the life typical of harsh, high-energy sites - delicate sea fans, innumerable, exquisite jewel anemones, extensive coverings of dead men's fingers and massive Devonshire cup corals, to name but a few of the better known creatures, clung to the rock, while sea cucumbers and urchins grazed over it. I saw large ross corals, and a ling, a fish I had only seen once before underwater; and more crawfish in a week's diving here than I have in the last 10 years. They seemingly had no fear of us (Irish law prohibits the taking of shellfish by divers).

Most of the sites were at 20-30m, so reasonable dive times could be had at the expense of fairly short stops. Swell was sometimes a problem, especially for the photographers as, in the coastal Atlantic, water movement is fairly strong. Light penetration, even on overcast days, was surprisingly high and torches were really only needed for watching under overhangs.