The movie is a love story between an Irish fisherman (Farrell) and a mermaid (Bachleda) – and at the opening night, from the red carpet to the Aveniu Wines-sponsored after-party at Soho's Beba restaurant, the couple avoided any outward public displays of affection. Instead, they chatted with those around them.
"We met on the set, and we were very professional and focused on our part and our jobs," said the Mexican-born, Polish actress Bachleda, 26. "The story itself is so beautiful … we really didn't have time to get our true emotions [on screen]."
For the Dublin-born Farrell, 33, the hardest part of his role didn't come from a blossoming relationship, but from having to master a particular Irish dialect – "one of the hardest accents I had to do, because I felt a national obligation not to [muck] it up."
He explained, "Even though Ireland is a small island, there are a plethora of dialects. I was more familiar with the American accent watching T.J. Hooker in CHiPs than I was with the Irish accent in this particular town. It was a very kind of impenetrable accent."
The Baby's Sitting UpWhile avoiding questions about their relationship, the pair beamed when asked about their 6-month old son, Henry Tadeusz Farrell.
"He's sitting up already and all smiles!," said Bachleda. "He's such a lovely baby."
As for Farrell, who also has a 6-year-old son, James, from a previous relationship with model Kim Bordenave, "I'm reading Dr. Seuss to him, because it's so much fun, but it's probably more for me than for him," said the actor. "But also some Roald Dahl and William Butler Yeats, fairy tales and stuff like that."
Meet Sandra Bullock's baby! For the whole story – including photos of her son Louis, an emotional interview about her breakup with Jesse James and her life as a new mom – pick up the new issue of PEOPLE, on newsstands Friday