In “A Marriage at Sea,” the journalist Sophie Elmhirst’s elegant and propulsive nonfiction debut about a married couple cast adrift for months on a raft, this tension is on full display. Maurice and Maralyn Bailey took to the seas from 1970s England, selling their suburban home to buy a boat and sail to New Zealand. Nine months into the trip, a sperm whale breached under their boat — called the Auralyn, a combination of their names — and it sank into the Pacific, leaving them stranded on a crude raft with an assortment of salvaged items, luckily including water, canned food, a camera — and a biography of King Richard III..........The implicit question asked by all survival stories — well, at least for me — is self-reflective. Who would I be in this scenario? Would I make it? If I could get through that, can I persevere through whatever feels impossible in my own life? In Elmhirst’s decision to frame the book around Maurice and Maralyn’s whole lives, rather than just the sensational details from the lifeboat, lies her implicit answer: It’s not that the rest of us might survive, but that we are already doing so. ---Blair Braverman, New York Times