We took each other then, in a savage, urgent silence, thrusting fiercely and finishing within moments, driven by a compulsion I didn't understand, but knew we must obey, or be lost to each other forever. It was not an act of love, but one of necessity, as though we knew that left alone, neither of us could stand. Our only strength lay in fusion, drowning the memories of death and non-rape in the flooding of the senses. (20.76)
This is kind of like an intense version of make-up sex, except Jamie and Claire aren't making up with each other, they're making up with life. Both of them almost died after being ambushed, so they're getting reacquainted with life after this near-death experience by getting it on by the river.