While on their honeymoon on the beach the scuba instructor asks if they want to scuba. In the background you can see Chinaman's Hat a small island off the north east shore of Oahu, Hi. This is not a part of St. Barts.
When the movie was filmed, Irving Feffer was the name of a Los Angeles Superior Court Judge in downtown Los Angeles. Judge Feffer's daughter-in-law, Elizabeth Feffer (now a Los Angeles Superior Court Judge), worked at 611 West Sixth Street in downtown Los Angeles. The building, now called 611 Place, was the site of the BASE jump in the movie.
In the beginning of the movie after Lisa and Reuben are wed they fly to the St. Barts airport. The aircraft shown landing at the airport lands on the "displaced thresh-hold" and not on the actual area of the runway designated for landing. Displaced thresh-holds at airports are used for taxiing and allow more room for take off but are not available for aircraft to land on.