Doolin pier is one of two ferry terminals to the Aran Islands (the other is Rossaveal in Galway). From Doolin you can get to all three islands, with the closest being Inisheer (the smallest), the medium being Inishmaan, and the furthest being Inishmore (the largest). Here is how to plan a day trip without wasting half of it on the boat.
The three islands
Inisheer (Inis Oirr in Irish): smallest, closest to the mainland, fifteen minute crossing from Doolin. Population about 250. You can walk every road on the island in an afternoon. There is a wrecked freighter on the south coast you can walk up to and a small castle on the hill. This is the easiest day trip.
Inishmaan (Inis Meain): the middle island, smallest population, and the only one where Irish is still the everyday language. Forty minute crossing from Doolin. Less developed for tourists, very quiet, has a Synge cottage and a few stone forts. Best for visitors who want a properly rural island day.
Inishmore (Inis Mor): largest, with the famous Dun Aengus stone fort on the cliff. About an hour by ferry from Doolin. Hire a bike at Kilronan pier for ten euro, ride the eight kilometres to Dun Aengus. Plan a full day for this island.
Which to choose for one day
Inishmore for the dramatic stone fort. Inisheer for a relaxed half-day with a beach. Inishmaan if you want a properly off-the-beaten-track Irish-speaking experience and you are happy with little infrastructure.
Practical booking
Doolin2Aran Ferries and Aran Island Ferries both run from Doolin. Book the day before in summer; the boats can be full by morning. There are usually three to four sailings a day per island, with the first leaving around 10 AM and the last return around 5 PM. Cost is about thirty euro round-trip per adult to Inisheer, more to the further islands.
The cliff cruise
Both ferry companies run a one-hour cliff cruise from Doolin pier as a separate boat trip. It does not land anywhere; it follows the foot of the Cliffs of Moher and back. It is one of the best things you can do in Clare and most visitors miss it. You can combine it with a ferry to Inisheer the same day.
Weather and seasickness
The Atlantic between Doolin and the islands can be rough. If the forecast is for a 30 km/h or higher wind, expect a bumpy crossing. The boats run unless conditions are dangerous, but if you get seasick easily, take medication an hour before sailing. Sit at the stern (back) of the boat, ideally outside if the weather permits.
What to bring
Layers. The islands are exposed and the temperature drops on a windy day. Sturdy shoes if you plan to walk to Dun Aengus, where the path is uneven. A waterproof. Your camera. Cash, as some smaller cafes on the islands are card-shy.