THE INNER REEF: 18-33mts

The dive

The Inner Reef is one of a pair of reefs that Waterworld, the dive centre at Scraggane Pier, works off Gurrig Island at the western end of the Magharee Islands. The centre's own description is of a kelp forest that meets the reef and drops away to thirty-three metres, a wall of solid clean rock about half a mile long that finishes on sand. Sponges, anemones and soft coral cover the rock. On the sand at the foot of the wall the centre reports electric ray and monkfish, and it lists lobster, crawfish, sea cucumber, dogfish and blue shark along the reef itself. Of those, lobster, dogfish and the sea cucumber Holothuria forskali are in the occurrence records for this pin; electric ray, monkfish and blue shark are not, and rest on the centre's account alone.

The nearest independent description of this rock is a BioMar survey station 330 m due north of the pin, dived on 20 May 1996 and logged as "NE of Gurrig Island". The surveyors found limestone bedrock thrown into ridges with intervening furrows, the furrows bottoming at about 21.6 m and the ridge tops rising to 18.7 m. The rock was heavily pitted and bored, red algae dominated it, and there was a notable lack of brown algae. They also recorded surprisingly few crustaceans and anemones on that patch, which is worth holding alongside the centre's account of the same reef. Diazona violacea, the football sea squirt, was recorded at the neighbouring Gurrig stations and appears in the occurrence records here.

This is boat diving only, ten to fifteen minutes out from Scraggane Pier at Fahamore on the Maharees peninsula. There is no shore access and no way to walk to it. The name is relative: the Inner Reef sits on the landward, north-east side of Gurrig, and the Outer Reef is a separate pin 730 m away on the seaward side. That matters for what you see, because the older Irish dive guide to the Maharees notes that winter Atlantic gales scour the south-west faces of these islands almost bare while the easterly faces carry kelp forest.

• Kelp forest on the reef top giving way to a clean rock wall
• Wall runs roughly half a mile and terminates on sand
• Sponge, anemone and soft-coral cover on the rock
• Ridge-and-furrow limestone recorded by the 1996 BioMar survey 330 m north
• Sand at the base is where the centre reports rays and monkfish

Conditions

Waterworld gives visibility here as about 40 m on very good days, around 20 m on average and about 7 m on bad ones; the Castlegregory village guide reproduces the same figures but caps the best days at 30 m, so 20 m is the number to plan on. Water runs about 8 °C at the start of the season and 17 to 18 °C in July, August and September. The boats leave Scraggane Pier at 9am and 11am and the run out is ten to fifteen minutes. What stops diving here is Atlantic weather rather than current: the Magharees are north-facing and unprotected, and the swell decides the day.

On current: Two sources disagree about how tidal the Maharees are and the conservative reading is that it depends which island you are on. Dublin University Sub-Aqua Club, which dived the group extensively in June 2009, records that the sites are "fairly non-tidal, even mid tide there is only a small drift". The older Dive Ireland guide to the same islands warns that around Inishtooskert, further east, there is a good current on the third and fourth hours of the tide and advises diving slack water. Waterworld tags the Inner Reef as a drift as well as a reef and wall dive. Plan for slack or a light drift and ask the boat which way it will run on the day.

Best months: May, Jun, Jul, Aug, Sep