This pair of islands lie off Penrhyn Du, Abersoch, and are a clear divider between the calm waters of Tremadog Bay and those of Porth Ceiriad and Porth Neigwl (Hell's Mouth) to the west. St Tudwal's Island west is home to the landmark lighthouse and is a long thin island and looks much smaller than it's neighbour from some angles, though the islands have a similar land mass overall. Sheep live on this island, somehow! St. Tudwal's Island east was once home to a monastery and attempts have been made to have communities living on the island, though these have failed and a small building is all that remains. Black rabbits have had better luck in living on the island and are still there now! The island is privately owned. Beyond the islands, to the east, are Carreg-y-Trai, or "half tide rocks" as they are often known by sailors, and this group of rocks could once have been a third island perhaps, but are now home to a fairly large seal colony and can often be seen from the coast on the horizon on low tides. On stormy days, huge waves breaking over the rocks are also visible from the mainland.

The difference between Maen Gwenonwy and all the other islands off Llŷn is that at low tide, it isn't actually an island. The island's close proximity to the coast means a bar has formed across to it. Maen Gwenonwy is located just off Porth Ysgo, to the northeast of the Gwylan Islands. Porth Cadlan is the connecting beach between the island and the mainland. The closest the public can get to Maen Gwenonwy is the top of the cliffs between the island and Porth Ysgo, attempts shouldn't be made to get on to the island from the land.

Ynysoedd Gwylan (Gwylan lit. seagull Islands)

Another pair of islands off the coast of Llŷn near Aberdaron, though these are much smaller than St. Tudwal's Islands off Abersoch. The island nearest the mainland is Ynys Gwylan Fawr ("fawr" meaning big/large) and the smaller of the two is Ynys Gwylan Bach ("bach" meaning small). The islands are well known for their large puffin population and their relative isolation allows wildlife out here to thrive. The waters around this part of the coast are famous for their currents, with the tides pushing their way up the Irish Sea, and there is often a small tidal flow between Ynys Gwylan Fawr and the mainland - but nothing like those that are seen in Swnt Enlli (the Bardsey Sound). The islands shelter Aberdaron Bay to any southerly or south-easterly waves, but not the prevailing swell from the south west, often making the beach popular with surfers.

Ynys Enlli (Bardsey Island)

Enlli has long been the destination for thousands of pilgrims - it is said to have 20,000 saints buried on the island, though this has been disputed! It was once said that three trips to Enlli was the equivalent to one trip to Rome. The treacherous waters between the island and the mainland have brought many ships to their end. Swnt Enlli (the Bardsey Sound) is one of the most dangerous stretches of water around the coast of Britain and the tide here can run at up to 9 knots. The sound is two miles wide, though the island often looks much closer when viewed from Mynydd Mawr on the mainland (see photo above). The lighthouse can also be seen from here and is a vital aid for sailors navigating the seas around the island. The island had a king until quiet recently and was bought by the present owners, the Bardsey Trust in 1979. Boat trips to the island are available from Pwllheli and Porth Meudwy, near Aberdaron.