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Suspension bridge at Ynys-y-Moch, Anglesey dive site - courtesy of Tony Gilbert
Suspension bridge at Ynys-y-Moch, Anglesey dive site - courtesy of Tony Gilbert
Suspension bridge at Ynys-y-Moch, Anglesey dive site - courtesy of Tony Gilbert
View of the Menai Striats at Ynys-y-Moch, Anglesey dive site - courtesy of Tony Gilbert
Sagartia anemones at Ynys-y-Moch, Anglesey dive site - courtesy of Tony Gilbert
Shore crabs at Ynys-y-Moch, Anglesey dive site - courtesy of Tony Gilbert

Scuba Diving North Wales, UK, Europe

Reader Reviews:

Dive Site: Ynys-y-Moch

Location: Menai Straits, North Wales

Description: Drift or shore dive

Depth: 0 - 15 metres (0 - 50 feet)

Visibility: 4 - 8 metres (13 - 26 feet)

Rating: ****

An exciting dive for the marine life in an area awash with dangerous currents. Luckily for me and many others in the northwest of England and North Wales, providing the tides are right the Menai Straits under or around the Menai Suspension Bridge provides the diver with an all-year-round shore dive site, guaranteed! The down side is when the tides are not right it's running at anything between 6 and 9 knots, but it's best to dive it at a slack period to appreciate the sheer vastness and bio-diversity of marine life. Screaming drifts can be had but really only with boat cover.

Don't take my word for it ask Bangor University of Ocean Sciences who regularly make studies of the area, especially under the Menai Suspension Bridge built by Thomas Telford in 1826. The Menai Straits in glacial times used to be estuarial, until afterwards when it became tidal bringing masses of nutrients along its length. The turbo-fed marine life thrives in this area and visibility is reduced as a result, but who cares its awesome to dive for the marine life!

Under the bridge is a small island called Pig Island and this forms an underwater nature trail usually dived from west to east as the tide flows afterwards. The first thing the diver encounters are sponge cliffs, stepped walls of rocks covered in solidified yellow custard is the best analogy. Look closer and one will find a plethora of filter feeding marine, both sessile and mobile. Lobsters are one thing but hundreds of crabs of differing varieties can be found. Throw in a load of dragonets, scorpionfish, yellow coloured scorpion spider crabs, gunnell, many pollack and shells and you have the makings of a good dive.

The depth starts at zero to a maximum of 15m and usually the bottom composition of terminal moraine is covered in dense carpets of very colourful and voracious dahlia anemones. In places huge beds of mussels dangle precariously off rock edges whilst at certain times of year masses of nudibranchs, particularly Dendronotus frondosus can be seen grazing.

The visibility can vary the average being 4m and sometimes it goes up to 8m. With this amount of marine life it's hardly surprising many of us divers crave this site all year round especially those with cameras with macro lenses fitted!

Tony Gilbert

I have only dived in salt water abroad and I do a lot of diving in the UK but always tends to be in quarries. I have read the review of this site and would like more information on the best times to go and more about the currents. I'm thinking of going up to this site over Christmas, can someone give me a little more info please as I'm bit of a novice when it comes to diving in the sea? This sounds like a fantastic site to dive....

Simon Stacey | 14/12/2008

Simon, I have dived this site a number of times with the author and it is an excellent site. However, in my opinion you need good experience before attempting it. A torch is absolutely mandatory and you must be confident with visibility less than 1m should it arise! The dive should ideally be carried out on neap tides anywhere between 3 to 3.5 hours before Liverpool Low Water. Oh and SMBs and dive knives are also mandatory!

Tony New | 14/04/2009

See "The Essential Underwater Guide to North Wales Volume One", by Chris Holden (See books on this site, or www.calgopublications.co.uk). This excellent book provides a wealth of information on diving around Lleyn and western Anglesey, including the Straits. I would however recommend before attempting any UK sea diving, regardless of whether you've sea-dived abroad or in UK quarries, that you see if your club can provide a "UK Sea diving orientation" course, preferably in a dry-suit. After which it is best to dive in more controlled surroundings first, either with your club from boat or shore on more mundane sites to gain the necessary experience, at least 20-30 dives like this. (You could always sign on a boat charter, eg. with Quest Charters or SBS Boat charters to do some of the diving in the area).

Then you may be ready for shore-diving the Straits - which should be attempted with a person who has already dived it. Get it wrong and you'll either end up in Liverpool or Ireland!

Tony Gilbert | 07/05/2009

"Guaranteed diving" was mentioned earlier, however there are certain conditions that may preclude diving. These include:

1) Very bad visibility - no visibility, which would make the diving not enjoyable. This can happen very occasionally when certain winds have blown, or there has been much heavy rain. Average vis is 4m, but can range up to +/- 4m! In Dec 2009, we had 8m+ visibility.

2) Dense Sea Fog - although it prob. doesn't stop the diving completely. If there are divers new to the site, it may be wise to dive in better surface conditions. If the fog is such that the opposite bank cannot be seen, then shore cover cannot see far away surfacing divers, nor boats. And if club diving check your liability and that of the club! Individuals can make their own choices of course, but the less 999/112 incidents the better. We encountered dense sea fog Feb 2010, with only half the bridge being seen.

Tony Gilbert | 10/02/2010

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