38 km

After a long break, he swam the 1 km in one go, finishing at 15:22. He's done 90% of the distance, and has 4.2 km left. I'm extrapolating a finish at 10:34 p.m. His stroke looks good (see video in previous post), he only had half a cookie between km 37 and 38. Rhonda says he's swimming on guts because he has nothing else in him.