Curise stop in Cork, Ireland (Cobb)

The city of Cobh (pronounced “Cove”) has a few sights - steep, atmospheric streets, a couple of small, nice art museums on the street lining the harbor, and a Titanic Experience museum that’s interesting but disorganized - but its biggest attraction is a scenic JFK park with a gazebo bandstand, bird dropping-covered benches, and a very popular ice cream stand. You could kill a couple of hours in Cobh itself, but for a whole day, head to Kinsale and take Barry’s Historic Stroll walking tour (at 9:15 and 11:15 in the morning) then visit the town longer, have lunch, or walk out to the old fort down past the harbor.

If you went to Cork city itself, see the amazing English Market - assemble a picnic lunch or have lunch at the excellent restaurant upstairs, and see the Crawford Art Gallery museum. The Blarney Castle is just north of Cork, and has interesting castle remains surrounded by fabulous gardens.

The train station to Cork could not be closer to the cruise dock. It is straight in front of you as you disembark.

Then from Cork (Kent) Station it is a short walk across the bridge into the City Centre. Like all mainline stations in Ireland Cork station is named after one of those nationalists involved in the Irish Civil War- in this case Thomas Kent who was executed after the 1916 Easter Uprising. There is an old steam locomotive on display in the station.

Back in Cobh a lung busting walk takes you up the hill to the Cathedral- worth the walk.

Walk beyond the Cathedral for about 20 minutes and you reach the Old Cemetery where almost 200 victims of the RMS Lusitania sinking by German torpedo are buried- with an impressive modern memorial.

In April this year I took a ship's excursion for a panoramic" (i e an extensive drive) tour in and through Cork and then a whiskey tour and tasting. It was a gloomy and slightly drippy day so not the prettiest although interesting. I had a ship credit so it was the best use of that credit.
Cobh had a small front street with one good charity shop, and more walking up the hill as other poster mentioned. Imho, not enough for a day.
I agree that the train could be more fun, Rome to Rio app says trains from Cobh to Cork are every 30 minutes and $4-6.
Waterford is usually mentioned as an excursion- you might look for a small group tour on Cruise Critic Roll Call.