As of 1st July, EU citizens (Irish included) are allowed to enter Croatia without proving the purpose of entry, while citizens of countries outside the European Union must prove the purpose of entry at border crossings.
What this means for Irish travellers:
Irish travellers can freely enter Croatia. They only need to fill in the form https://entercroatia.mup.hr/ to announce their visit and to help speed up the process at the border, but they no longer need to have proof of accommodation booking to present at the border.
Please also note that as of last week, masks are mandatory on public transport, ferries included.
General announcement re borders can be found here: https://www.koronavirus.hr/latest-news/lifting-travel-restrictions-on-croatian-borders/720