I think the others above have given some really good advice. It's good that the lad can feel relaxed enough in your company to "sprawl" etc ! May I suggest that you join in on the swimming activities - it sounds like fun ! Why not suggest that the lad cooks tea for all of you, say one night a week. It wouldn't have to be anything complicated, say something like beans on toast at first, you two could show him more advanced stuff later, that will help him to learn to look after himself. Suggest switching off the tv and playing some games, or devising the menus for next week and the necessary shopping required. I'm sure if you got to know him better you'd feel a lot more comfortable with him around.