Work as hard as I can to survive with him.
We'll need to create a shelter. One of us will stay in the shelter while the other searches for a source of water. That person will make marks in the sand so he will know where to walk back. If he doesn't find water after a big amount of time, they'll come back. The person in the shelter should be looking for animals, but still staying at the shelter.
..then we'll die from a bad plan.