OverHang 16-20mts

The dive

OverHang is one of the named dive sites Waterworld publishes for the Maharees, the island group known in English as the Seven Hogs off the northern tip of the Castlegregory sand spit in Co. Kerry. The centre's own site list groups it with The Cross Roads, the Letter Box, the Inner Reef and the Outer Reef under Gurrig Island, and this pin sits about 150 m from Gurrig Island itself. The name, and the 16-20 m in it, are the operator's label for one piece of that island's underwater rock rather than anything you would find on a chart - which makes the operator the primary and effectively the only source for the site.

What they describe is a rock face carpeted in anemones - dahlia, plumose, rosea and jewel - with dead men's fingers in orange and white, urchins burrowed into the solid rock, edible and spiny spider crabs living in the cave, and topknot flatfish camouflaged against the vertical walls and overhangs. Dublin University Sub-Aqua Club's independent guide to Gurrig Island lines up with that: a maximum around 20 m, a rock face on the north-west side that opens into a very large gully with resident lobsters and shoals of fish, walls of soft coral and anemones, and kelp areas with swim-throughs.

Getting there is easy by Irish standards. Waterworld run two boat dives a day, at 09:00 and 11:00, from Scraggane Pier at Fahamore - the centre is about 30 m from the pier - and the islands are a 10 to 15 minute run out. The centre gives visibility of about 40 m on the best days, around 20 m on average and about 7 m on bad ones, with water from 8 degrees C at the start of the dive season up to 17 or 18 degrees in July, August and September. DUSAC found the ground fairly non-tidal, with only a small drift even at mid tide, and Scraggane's two slips easy to launch and retrieve from except at very low water.

There is one more, older and much harder-edged source for this ground. The 1996 BioMar survey put three dated dive stations around Gurrig Island, all within about 600 m of this pin: limestone bedrock thrown into ridges with furrows between them, heavily pitted and bored, running from roughly 19 m down past 28 m, covered in foliose red algae with dead men's fingers, Devonshire cup coral and the sea squirt Diazona violacea on it. The station south-west of the island records that considerable surge was felt. That is worth knowing before you go into an overhang or a cave here.

• Dahlia, plumose, rosea and jewel anemones carpeting the rock
• Dead men's fingers in orange and white
• Urchins burrowed into the solid rock
• Topknot flatfish flattened against the vertical walls and overhangs
• Edible and spiny spider crab inside the cave

Conditions

Cold Atlantic water on an offshore island group. Waterworld quote visibility of about 40 m on the best days, 20 m on average and around 7 m on the worst, with water from 8 degrees C at the start of the dive season up to 17 or 18 degrees in July to September. Boats run twice a day from Scraggane Pier and DUSAC found the ground fairly non-tidal with only a small drift at mid tide.

On current: The sources disagree and the conservative reading is the one to plan on. DUSAC call the Maharees ground fairly non-tidal, with only a small drift even at mid tide. NPWS, describing the same islands, records moderately strong currents between them, and says the wave-exposed reefs at 19-28 m carry a foliose red algal community that indicates tide-swept habitat; the 1996 BioMar stations in the sounds recorded moderately strong tidal streams and current-swept ground. Expect moderate flow between the islands even though the rock faces themselves are quieter, and plan the dive rather than assume slack. Separately, swell is what actually cancels days here: the BioMar station south-west of Gurrig Island recorded considerable surge, and the operator's own warning about the cave entrances at the neighbouring Gully site is specifically about swell.

Best months: Jul, Aug, Sep