Night Swimmers by Roisin Maguire

Grace lives alone in a coastal village in Northern Ireland, filling her days with wild swimming, fishing, quilting and baiting the tourists who blow in from the city.

One of the visitors is Evan, on an enforced holiday from his family in Belfast as he grieves the death of his infant daughter. But before a week is out, he is trapped there by lockdown. When Grace grudgingly saves Evan from drowning, and his reserved young son arrives unexpectedly, all three are startled into a reckoning with their past and a reconnection with the outside world.