The actress plays Ruby Buckton in the soap, while Luke plays surf hunk Romeo Smith.
Asked by TV Week what he is like as a boyfriend, Rebecca said: "How long have you got? I don't know where to start!"
She went on: "We laugh together and we're comfortable together. He's always very level-headed and I'll be bouncing off the walls, so he complements me well.
"He's caring, supportive and an amazing friend. We've built a great friendship and that's really important to me."
Luke previous said there was "not much to not like" about his girlfriend.