2. is correct. I have never heard of 1. It's not standard UK English. Can you post the context?

2) "Fluke" means a surprising, unexpected chance event that probably will never happen again. Usually it means a piece of good luck. "I tossed the basketball over my shoulder without looking, and it went into the net. Just a fluke." 1) As a U.S. native speaker I had never heard of "fluke trip" before. It turns out that "fluke" is another name for the kind of fish I call a "flounder." They are sometimes called "flatfish." The genus name for this kind of fish is Paralichthys, they lie flat on the ocean bottom, and their body shape has evolved in a curious way so that both eyes are on the same side of their head. I've never fished for them, but I've had them in restaurants and they are deliciious. It's odd that I didn't recognize the term, because I Googled I found charter fishing boats offering "fluke trips" out of Nantucket, which is not too far from where I live!