WHEN I GO ON A DIVING HOLIDAY, the thing I most want is to go diving. Guaranteed diving, no matter what.
Details such as comfortable accommodation, a friendly and well-equipped dive centre, easy loading and unloading of the boat, good pubs and restaurants for eating out in the evenings, and attractive countryside above water all help to make a good holiday, but diving is what its all about.
Even when the sky is cloudy, the rain falling and the wind blowing, a decent dive keeps my gills wet and stops me getting antsy with cabin fever.
Not that the sun doesnt shine in Donegal. I arrive to a near-perfect day of gentle waves and clear sunshine to kick the trip off with a couple of dives on the Laurentic, a 14,892-ton White Star liner converted to an armed merchant cruiser during World War One.
Having just returned from three days surveying the Moldavia, the only slightly smaller liner and armed merchant cruiser torpedoed off Sussex, I wonder if I can use this experience to sketch the Laurentic. Its just an outside hope, as my host Donald Cullen at the Mevagh Diving Centre has already explained that the wreck had been well dispersed and turned over by salvors.
In 1910, Laurentic hit the headlines when the captain of the White Star liner Montrose, en route to Canada, recognised two of his passengers as the fugitive murderer Dr Crippen and his lover Ethel Le Neve. His wireless telegraph alerted Scotland Yard.
An Inspector Drew boarded Montroses sister-ship Laurentic which, being fitted with a low-pressure turbine and third shaft, was faster. She arrived in Canada a day before the Montrose, allowing Drew to arrest Crippen.
When the Laurentic left Liverpool seven years later, its cargo included 3211 bars of gold bullion, then worth £5 million (about £700m today), destined to pay for munitions from America.
On the night of 25 January, 1917, she struck two moored mines laid in the entrance to Lough Swilly by U80, and sank in 45 minutes. Most of the crew made it into the lifeboats, though many died of exposure.
Over the next seven years, Royal Navy hardhat divers recovered all but 25 bars of gold from the collapsing wreck. Twenty bars remain unaccounted for.

TWO DIVES LATER and I know my way round the Laurentic, but have given up thinking of a sketch within minutes of my arrival. The most intact part is the bow. If you want armaments, behind the bow on the port side one of the 4.7in guns stands clear of the seabed pointing towards the surface, and the mount and breech of another can be seen partly dug into the silt. The corresponding store of ammunition is across the wreck, just above the keel.
Also significant are the engines, with a central shaft driven by a low-pressure turbine, using residual steam from the pair of expansion engines driving shafts to either side. With the wreck completely broken open, much of this machinery is visible further aft and close to the keel.
At this point, you could be forgiven for thinking that I would be heading further offshore to dive wrecks in trimix territory. In fact, at 38m down, the Laurentic is a deep anomaly in an otherwise shallow trip, where I enjoy scenery and marine life on reefs, walls and canyons, all in less than 25m.
I am here to evaluate Donegal as a general diving holiday destination.
We do visit another wreck site, the steamship Kalliopi, torpedoed on 7 October, 1943, catching fire and drifting onto a reef a few hundred metres off Melmor Head. The wreck now lies devastated by the Atlantic, and there is plenty to see, including the remains of the engine and three reasonably intact boilers. However, it is the shallow gullies and canyons under the rock that provide the most interest.
On Melmore Head, a much larger canyon provides the scenic highlight of the trip. Vis that is poor by local standards at 15m shows off a canyon about 5m wide and 10m deep, its floor at 25m. I flit from side to side, picking on outcrops with the best coverings of anemones and soft corals, then move on to a dogfish snoozing on a ledge.
As the canyon opens out, we follow the wall round the headland. A rock fissure opens into a nice little cave, exited by a chimney to the shallows above. Its a convenient spot to run off the few minutes of decompression my buddy has accumulated.
On a rougher day, but still with good sunshine, we dive shallower canyons beneath the more sheltered Stags, tucked in behind Horn Head.
There is no point trying to get below the kelp line, but the kelp cant survive on the overhanging walls, so anemones and soft corals abound in easy shallow water. Crabs of all kinds take advantage of cracks in the rocks, and cuckoo wrasse make a point of being nosy.

ON THE MORE SHELTERED Pat Macgees Reef, I start close to the sandy seabed. I am disappointed by the stirred-up visibility and partly scoured rocks, yet only a few metres up the reef the water clears, and more overhanging ledges provide top-quality habitats for all sorts of colourful sessile animals.
In the evenings, Guinness, whiskey and dinner are well served only a short walk into the centre of Carrigart, by the restaurants and bars of the Carrigart Hotel and the North Star Inn. Cormick, manager of the hotel, is a keen diver, and often dives with Mevagh Diving Centre.
A few miles drive beyond town, the Olde Glen Bar won a 2008 Pub of the Year accolade. Once dinner is over, local musicians gather there to play a mixture of traditional and modern music.
Donald generally launches the RIB at a boatyard about 10 minutes drive from the dive centre.
From here, we began the week by heading out from the convoluted lough of Mulroy Bay to dive in the open sea.
But as the wind picks up and the weather closes in, we head instead further into the lough, beneath the construction of a new bridge spanning the narrowest part and into the wider and deeper water of Mulroy Bay proper.
Here, among the mussel farms, we dive in 5m visibility on reefs where the marine life is just as prolific, but interestingly different from that of the open Atlantic.
This is muck-diving Irish style, so I dive with a macro lens and have no trouble finding things to interest me for several hour-long dives. With rain falling above, it is actually much nicer under water.
The weather front passes through, and conditions improve for my last day. The sea is not fully settled, but that doesnt matter, as the tides are right for a drift-dive at Dundrooan.
This small reef guarding the entrance to Mulroy Bay, marked by a green starboard beacon and light, is one of those places that begs to be dived.
On our first trip out to the Laurentic I had asked Donald about the current screaming through as the RIB kicked its way between whirlpools.
While the channel is generally only 10-12m deep, by the beacon the reef is scoured down to 25m. Yes, it is an excellent dive, Donald had told me, but only on the right incoming tide.

SUCH A DAY ARRIVES, so we watch the ebbing tide slacken, and begin to change as Donald gives the briefing. No SMBs are needed, as long as we stay on the reef. We should have enough slack to hit the bottom and zigzag a few times to follow the reef up before the current builds to peel us off. This is the time to pop a delayed SMB and relax, while drifting into the safe waters of the lough.
As expected, the marine life is tight against the rock and dense. Anemones, soft corals, sponges, hydroids and bryozoans leave little real estate undeveloped. Every big crack has a lobster or a conger eel, sometimes sharing. Every small crack has a monster crab. It may prefer a bigger crack, but the space is already taken.
Drifting off with the now-relentless flooding tide, I drift for five minutes past horizontal kelp, and teams of dogfish flying in formation.
The sea conditions look set to improve further. Donald has full bookings for the Laurentic and other offshore dives at the weekend, but I have a ferry to catch. It is a 150-minute drive to Belfast, where I board the Norfolk Lines overnight ferry to Birkenhead.
I make sure to top up my van with cheap fuel before crossing the border back to Northern Ireland. You can tell where the border is - the Republic side is all petrol stations, and the Northern Ireland side is not.
Even with cheaper Irish fuel, in these days of rising prices, taking a longer ferry route makes even more sense when it saves miles of driving.
Add in a nights accommodation on board and the reduced miles to drive, and it certainly makes a good end to any trip to the Emerald Isle.

FACTFILE
GETTING THERE: Norfolk Line Irish Sea Ferry Services, Liverpool (Birkenhead) to Belfast, 0870 600 4321, www.norfolkline.com. From Belfast take the M2, M22 and A6 to Derry. Go north of Derry on the A515 to join the A2 into Eire, where the road becomes the N13 then N14 to Letterkenny. In Letterkenny, turn right on the R245 via Ramelton and Milford to Carrigart. Mevagh Diving Centre is on the right about 250m before the centre of Carrigart. If you prefer to fly from London Stansted to Derry or Belfast, the dive centre can arrange transfers.
DIVING & ACCOMMODATION: Mevagh Dive Centre, 00 353 (0)74 9154 708, www.mevaghdiving.com.
when to go As in the UK, but diving is available year-round.
MONEY: Euro.
PRICES: Mevagh Dive Centre offers a package of seven nights B&B with 10 boat dives and air fills for 520 euros, or 545 euros with tanks and weights. Discounts are available for large groups and booking before the end of January. The ferry from Birkenhead to Belfast costs from £75 each way for car and driver, including meals.
FURTHER INFORMATION: www.discoverireland.com. Shipwrecks of the Irish Coast by Edward J Bourke, Vols 1 & 2. Irish Wrecks Online by Randall Armstong, www.irishwrecksonline.net.