Under by Diana Knightley

The world is just one giant tire fire of awful and Beckett has to do what seems impossible. Keep Luna safe…
But there are terrible storms, oppressive governments, and endless war, standing in his way.
Beckett and Luna are headed to shore.
They have a plan — to live in his house, together, on a mountain. The trouble is, they aren’t together now.
Luna is alone, paddling across the unrelenting ocean, meeting an unknown future with only her basic gear: a paddleboard, food and water, a tent.

Their communication is by radio, but that’s spotty, especially when the storms are coming…