In Ireland, the national language is Irish Gaelic or Gaelic. Their constitution is in Gaelic, so every new law or rule must be written in the language. Most of the Irish people speak English, though, which is the unofficial language. Great Britain brought the language over centuries ago when it was occupying Ireland. Only a few places in Ireland speak mostly Gaelic today. School children are taught the language all over the country until about sixth grade.
Ireland uses the euro, the same currency adopted by The Netherlands and other European countries. Later that week I was in Poland, where they use the Polish zloty. One euro is equivalent to just over four Polish zloty.
In Ireland, the average price of a bottle of water is 2.50 euros, which is pretty comparable to the Dutch price. However, in both countries, you can always buy a bottle of water for a cheaper price in some grocery stores. The prices are usually higher at conveniences stores or other stores located at the airport or train stations.