Don't worry, I still get in some good seafood here. I often enjoy a variety of fish prepared other ways including grilled or baked. I have had many tasty fillets of haddock, cod, pollack, and Atlantic salmon. All of these I highly recommend!
Cockles and mussels must first be soaked in cold water to allow for the grit to shed off them. After they've soaked, these bivalves must be rinsed off before they're cooked. The cooking is pretty easy since you just steam them for a few minutes and all the shells pop open. Some people eat them straight out of the shell without anything, although many also dip them in a little sauce of some kind even if it's just vinegar.
This food is VERY much connected to the local environment. Remember, Ireland is an island, so seafood is a-plenty! There are many fishing towns along the coast which have inspired literature and songs about fishermen, the sea and seafood. One famous Irish song, "Molly Malone", is sometimes called "Cockles and Mussels" since the song talks about Molly Malone selling them. Perhaps you can pull up the song on Youtube and listen to it. There is even a statue of Molly Malone in the City Centre of Dublin. As you can see, the Irish people's connection to the sea is very much a part of the culture, here.
